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  1. Aug 01, 2024
  3. Jul 30, 2024
  5. Jul 29, 2024
    • Filipe Manana's avatar
      btrfs: fix corruption after buffer fault in during direct IO append write · 939b656b
      Filipe Manana authored 
      During an append (O_APPEND write flag) direct IO write if the input buffer
was not previously faulted in, we can corrupt the file in a way that the
final size is unexpected and it includes an unexpected hole.

The problem happens like this:

1) We have an empty file, with size 0, for example;

2) We do an O_APPEND direct IO with a length of 4096 bytes and the input
   buffer is not currently faulted in;

3) We enter btrfs_direct_write(), lock the inode and call
   generic_write_checks(), which calls generic_write_checks_count(), and
   that function sets the iocb position to 0 with the following code:

	if (iocb->ki_flags & IOCB_APPEND)
		iocb->ki_pos = i_size_read(inode);

4) We call btrfs_dio_write() and enter into iomap, which will end up
   calling btrfs_dio_iomap_begin() and that calls
   btrfs_get_blocks_direct_write(), where we update the i_size of the
   inode to 4096 bytes;

5) After btrfs_dio_iomap_begin() returns, iomap will attempt to access
   the page of the write input buffer (at iomap_dio_bio_iter(), with a
   call to bio_iov_iter_get_pages()) and fail with -EFAULT, which gets
   returned to btrfs at btrfs_direct_write() via btrfs_dio_write();

6) At btrfs_direct_write() we get the -EFAULT error, unlock the inode,
   fault in the write buffer and then goto to the label 'relock';

7) We lock again the inode, do all the necessary checks again and call
   again generic_write_checks(), which calls generic_write_checks_count()
   again, and there we set the iocb's position to 4K, which is the current
   i_size of the inode, with the following code pointed above:

        if (iocb->ki_flags & IOCB_APPEND)
                iocb->ki_pos = i_size_read(inode);

8) Then we go again to btrfs_dio_write() and enter iomap and the write
   succeeds, but it wrote to the file range [4K, 8K), leaving a hole in
   the [0, 4K) range and an i_size of 8K, which goes against the
   expectations of having the data written to the range [0, 4K) and get an
   i_size of 4K.

Fix this by not unlocking the inode before faulting in the input buffer,
in case we get -EFAULT or an incomplete write, and not jumping to the
'relock' label after faulting in the buffer - instead jump to a location
immediately before calling iomap, skipping all the write checks and
relocking. This solves this problem and it's fine even in case the input
buffer is memory mapped to the same file range, since only holding the
range locked in the inode's io tree can cause a deadlock, it's safe to
keep the inode lock (VFS lock), as was fixed and described in commit
51bd9563

 ("btrfs: fix deadlock due to page faults during direct IO
reads and writes").

A sample reproducer provided by a reporter is the following:

   $ cat test.c
   #ifndef _GNU_SOURCE
   #define _GNU_SOURCE
   #endif

   #include <fcntl.h>
   #include <stdio.h>
   #include <sys/mman.h>
   #include <sys/stat.h>
   #include <unistd.h>

   int main(int argc, char *argv[])
   {
       if (argc < 2) {
           fprintf(stderr, "Usage: %s <test file>\n", argv[0]);
           return 1;
       }

       int fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC | O_DIRECT |
                     O_APPEND, 0644);
       if (fd < 0) {
           perror("creating test file");
           return 1;
       }

       char *buf = mmap(NULL, 4096, PROT_READ,
                        MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
       ssize_t ret = write(fd, buf, 4096);
       if (ret < 0) {
           perror("pwritev2");
           return 1;
       }

       struct stat stbuf;
       ret = fstat(fd, &stbuf);
       if (ret < 0) {
           perror("stat");
           return 1;
       }

       printf("size: %llu\n", (unsigned long long)stbuf.st_size);
       return stbuf.st_size == 4096 ? 0 : 1;
   }

A test case for fstests will be sent soon.

Reported-by: default avatarHanna Czenczek <hreitz@redhat.com>
Link: https://lore.kernel.org/linux-btrfs/0b841d46-12fe-4e64-9abb-871d8d0de271@redhat.com/
Fixes: 8184620a

 ("btrfs: fix lost file sync on direct IO write with nowait and dsync iocb")
CC: stable@vger.kernel.org # 6.1+
Tested-by: default avatarHanna Czenczek <hreitz@redhat.com>
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      939b656b
    • Naohiro Aota's avatar
      btrfs: zoned: fix zone_unusable accounting on making block group read-write again · 8cd44dd1
      Naohiro Aota authored 
      When btrfs makes a block group read-only, it adds all free regions in the
block group to space_info->bytes_readonly. That free space excludes
reserved and pinned regions. OTOH, when btrfs makes the block group
read-write again, it moves all the unused regions into the block group's
zone_unusable. That unused region includes reserved and pinned regions.
As a result, it counts too much zone_unusable bytes.

Fortunately (or unfortunately), having erroneous zone_unusable does not
affect the calculation of space_info->bytes_readonly, because free
space (num_bytes in btrfs_dec_block_group_ro) calculation is done based on
the erroneous zone_unusable and it reduces the num_bytes just to cancel the
error.

This behavior can be easily discovered by adding a WARN_ON to check e.g,
"bg->pinned > 0" in btrfs_dec_block_group_ro(), and running fstests test
case like btrfs/282.

Fix it by properly considering pinned and reserved in
btrfs_dec_block_group_ro(). Also, add a WARN_ON and introduce
btrfs_space_info_update_bytes_zone_unusable() to catch a similar mistake.

Fixes: 169e0da9

 ("btrfs: zoned: track unusable bytes for zones")
CC: stable@vger.kernel.org # 5.15+
Signed-off-by: default avatarNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      8cd44dd1
    • Naohiro Aota's avatar
      btrfs: do not subtract delalloc from avail bytes · d89c285d
      Naohiro Aota authored 
      The block group's avail bytes printed when dumping a space info subtract
the delalloc_bytes. However, as shown in btrfs_add_reserved_bytes() and
btrfs_free_reserved_bytes(), it is added or subtracted along with
"reserved" for the delalloc case, which means the "delalloc_bytes" is a
part of the "reserved" bytes. So, excluding it to calculate the avail space
counts delalloc_bytes twice, which can lead to an invalid result.

Fixes: e50b122b

 ("btrfs: print available space for a block group when dumping a space info")
CC: stable@vger.kernel.org # 6.6+
Signed-off-by: default avatarNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: default avatarBoris Burkov <boris@bur.io>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      d89c285d
    • Boris Burkov's avatar
      btrfs: make cow_file_range_inline() honor locked_page on error · 47857437
      Boris Burkov authored 
      
The btrfs buffered write path runs through __extent_writepage() which
has some tricky return value handling for writepage_delalloc().
Specifically, when that returns 1, we exit, but for other return values
we continue and end up calling btrfs_folio_end_all_writers(). If the
folio has been unlocked (note that we check the PageLocked bit at the
start of __extent_writepage()), this results in an assert panic like
this one from syzbot:

  BTRFS: error (device loop0 state EAL) in free_log_tree:3267: errno=-5 IO failure
  BTRFS warning (device loop0 state EAL): Skipping commit of aborted transaction.
  BTRFS: error (device loop0 state EAL) in cleanup_transaction:2018: errno=-5 IO failure
  assertion failed: folio_test_locked(folio), in fs/btrfs/subpage.c:871
  ------------[ cut here ]------------
  kernel BUG at fs/btrfs/subpage.c:871!
  Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
  CPU: 1 PID: 5090 Comm: syz-executor225 Not tainted
  6.10.0-syzkaller-05505-gb1bc554e009e #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
  Google 06/27/2024
  RIP: 0010:btrfs_folio_end_all_writers+0x55b/0x610 fs/btrfs/subpage.c:871
  Code: e9 d3 fb ff ff e8 25 22 c2 fd 48 c7 c7 c0 3c 0e 8c 48 c7 c6 80 3d
  0e 8c 48 c7 c2 60 3c 0e 8c b9 67 03 00 00 e8 66 47 ad 07 90 <0f> 0b e8
  6e 45 b0 07 4c 89 ff be 08 00 00 00 e8 21 12 25 fe 4c 89
  RSP: 0018:ffffc900033d72e0 EFLAGS: 00010246
  RAX: 0000000000000045 RBX: 00fff0000000402c RCX: 663b7a08c50a0a00
  RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
  RBP: ffffc900033d73b0 R08: ffffffff8176b98c R09: 1ffff9200067adfc
  R10: dffffc0000000000 R11: fffff5200067adfd R12: 0000000000000001
  R13: dffffc0000000000 R14: 0000000000000000 R15: ffffea0001cbee80
  FS:  0000000000000000(0000) GS:ffff8880b9500000(0000)
  knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f5f076012f8 CR3: 000000000e134000 CR4: 00000000003506f0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
  <TASK>
  __extent_writepage fs/btrfs/extent_io.c:1597 [inline]
  extent_write_cache_pages fs/btrfs/extent_io.c:2251 [inline]
  btrfs_writepages+0x14d7/0x2760 fs/btrfs/extent_io.c:2373
  do_writepages+0x359/0x870 mm/page-writeback.c:2656
  filemap_fdatawrite_wbc+0x125/0x180 mm/filemap.c:397
  __filemap_fdatawrite_range mm/filemap.c:430 [inline]
  __filemap_fdatawrite mm/filemap.c:436 [inline]
  filemap_flush+0xdf/0x130 mm/filemap.c:463
  btrfs_release_file+0x117/0x130 fs/btrfs/file.c:1547
  __fput+0x24a/0x8a0 fs/file_table.c:422
  task_work_run+0x24f/0x310 kernel/task_work.c:222
  exit_task_work include/linux/task_work.h:40 [inline]
  do_exit+0xa2f/0x27f0 kernel/exit.c:877
  do_group_exit+0x207/0x2c0 kernel/exit.c:1026
  __do_sys_exit_group kernel/exit.c:1037 [inline]
  __se_sys_exit_group kernel/exit.c:1035 [inline]
  __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1035
  x64_sys_call+0x2634/0x2640
  arch/x86/include/generated/asm/syscalls_64.h:232
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
  RIP: 0033:0x7f5f075b70c9
  Code: Unable to access opcode bytes at
  0x7f5f075b709f.

I was hitting the same issue by doing hundreds of accelerated runs of
generic/475, which also hits IO errors by design.

I instrumented that reproducer with bpftrace and found that the
undesirable folio_unlock was coming from the following callstack:

  folio_unlock+5
  __process_pages_contig+475
  cow_file_range_inline.constprop.0+230
  cow_file_range+803
  btrfs_run_delalloc_range+566
  writepage_delalloc+332
  __extent_writepage # inlined in my stacktrace, but I added it here
  extent_write_cache_pages+622

Looking at the bisected-to patch in the syzbot report, Josef realized
that the logic of the cow_file_range_inline error path subtly changing.
In the past, on error, it jumped to out_unlock in cow_file_range(),
which honors the locked_page, so when we ultimately call
folio_end_all_writers(), the folio of interest is still locked. After
the change, we always unlocked ignoring the locked_page, on both success
and error. On the success path, this all results in returning 1 to
__extent_writepage(), which skips the folio_end_all_writers() call,
which makes it OK to have unlocked.

Fix the bug by wiring the locked_page into cow_file_range_inline() and
only setting locked_page to NULL on success.

Reported-by: default avatar <syzbot+a14d8ac9af3a2a4fd0c8@syzkaller.appspotmail.com>
Fixes: 0586d0a8

 ("btrfs: move extent bit and page cleanup into cow_file_range_inline")
CC: stable@vger.kernel.org # 6.10+
Reviewed-by: default avatarQu Wenruo <wqu@suse.com>
Signed-off-by: default avatarBoris Burkov <boris@bur.io>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      47857437
    • Chen Ni's avatar
      xfs: convert comma to semicolon · 7bf888fa
      Chen Ni authored 
      Replace a comma between expression statements by a semicolon.

Fixes: 178b48d5

 ("xfs: remove the for_each_xbitmap_ helpers")
Signed-off-by: default avatarChen Ni <nichen@iscas.ac.cn>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarChandan Babu R <chandanbabu@kernel.org>
      7bf888fa
    • Chen Ni's avatar
      xfs: convert comma to semicolon · 8c2263b9
      Chen Ni authored 
      
Replace a comma between expression statements by a semicolon.

Signed-off-by: default avatarChen Ni <nichen@iscas.ac.cn>
Fixes: 8f4b980e

 ("xfs: pass the attr value to put_listent when possible")
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarChandan Babu R <chandanbabu@kernel.org>
      8c2263b9
  7. Jul 28, 2024
  9. Jul 27, 2024
  11. Jul 26, 2024
  13. Jul 25, 2024
    • Filipe Manana's avatar
      btrfs: fix corrupt read due to bad offset of a compressed extent map · de9f46cb
      Filipe Manana authored 
      If we attempt to insert a compressed extent map that has a range that
overlaps another extent map we have in the inode's extent map tree, we
can end up with an incorrect offset after adjusting the new extent map at
merge_extent_mapping() because we don't update the extent map's offset.

For example consider the following scenario:

1) We have a file extent item for a compressed extent covering the file
   range [108K, 144K) and currently there's no corresponding extent map
   in the inode's extent map tree;

2) The inode's size is 141K;

3) We have an encoded write (compressed) into the file range [120K, 128K),
   which overlaps the existing file extent item. The encoded write creates
   a matching extent map, adds it to the inode's extent map tree and
   creates an ordered extent for it.

   Note that the corresponding file extent item is added to the subvolume
   tree only when the ordered extent completes (when executing
   btrfs_finish_one_ordered());

4) We have a write into the file range [160K, 164K).

   This writes increases the i_size of the file, and there's a hole
   between the current i_size (141K) and the start offset of this write,
   and since the old i_size is in the middle of the block [140K, 144K),
   we have to write zeroes to the range [141K, 144K) (3072 bytes) and
   therefore dirty that page.

   We then call btrfs_set_extent_delalloc() with a start offset of 140K.
   We then end up at btrfs_find_new_delalloc_bytes() which will call
   btrfs_get_extent() for the range [140K, 144K);

5) The btrfs_get_extent() doesn't find any extent map in the inode's
   extent map tree covering the range [140K, 144K), so it searches the
   subvolume tree for any file extent items covering that range.

   There it finds the file extent item for the range [108K, 144K),
   creates a compressed extent map for that range and then calls
   btrfs_add_extent_mapping() with that extent map and passes the
   range [140K, 144K) via the "start" and "len" parameters;

6) The call to add_extent_mapping() done by btrfs_add_extent_mapping()
   fails with -EEXIST because there's an extent map, created at step 2
   for the [120K, 128K) range, that covers that overlaps with the range
   of the given extent map ([108K, 144K)).

   Then it does a lookup for extent map from step 2 add calls
   merge_extent_mapping() to adjust the input extent map ([108K, 144K)).
   That adjust the extent map to a start offset of 128K and a length
   of 16K (starting just after the extent map from step 2), but it does
   not update the offset field of the extent map, leaving it with a value
   of zero instead of updating to a value of 20K (128K - 108K = 20K).

   As a result any read for the range [128K, 144K) can return
   incorrect data since we read from a wrong section of the extent (unless
   both the correct and incorrect ranges happen to have the same data).

So fix this by changing merge_extent_mapping() to update the extent map's
offset even if it's compressed. Also add a test case to the self tests.
This didn't happen before the patchset that does big changes in the extent
map structure (which includes the commit in the Fixes tag below) because
we kept track of the original start offset in the extent map (member
"orig_start") so we could always calculate the correct offset by
subtracting that offset from the start offset.

A test case for fstests that triggered this problem using send/receive
with compressed writes will be added soon.

Fixes: 3d2ac992

 ("btrfs: introduce new members for extent_map")
Reviewed-by: default avatarQu Wenruo <wqu@suse.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      de9f46cb
    • Qu Wenruo's avatar
      btrfs: tree-checker: validate dref root and objectid · f333a3c7
      Qu Wenruo authored 
      
[CORRUPTION]
There is a bug report that btrfs flips RO due to a corruption in the
extent tree, the involved dumps looks like this:

 	item 188 key (402811572224 168 4096) itemoff 14598 itemsize 79
 		extent refs 3 gen 3678544 flags 1
 		ref#0: extent data backref root 13835058055282163977 objectid 281473384125923 offset 81432576 count 1
 		ref#1: shared data backref parent 1947073626112 count 1
 		ref#2: shared data backref parent 1156030103552 count 1
 BTRFS critical (device vdc1: state EA): unable to find ref byte nr 402811572224 parent 0 root 265 owner 28703026 offset 81432576 slot 189
 BTRFS error (device vdc1: state EA): failed to run delayed ref for logical 402811572224 num_bytes 4096 type 178 action 2 ref_mod 1: -2

[CAUSE]
The corrupted entry is ref#0 of item 188.
The root number 13835058055282163977 is beyond the upper limit for root
items (the current limit is 1 << 48), and the objectid also looks
suspicious.

Only the offset and count is correct.

[ENHANCEMENT]
Although it's still unknown why we have such many bytes corrupted
randomly, we can still enhance the tree-checker for data backrefs by:

- Validate the root value
  For now there should only be 3 types of roots can have data backref:
  * subvolume trees
  * data reloc trees
  * root tree
    Only for v1 space cache

- validate the objectid value
  The objectid should be a valid inode number.

Hopefully we can catch such problem in the future with the new checkers.

Reported-by: default avatarKai Krakow <hurikhan77@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/CAMthOuPjg5RDT-G_LXeBBUUtzt3cq=JywF+D1_h+JYxe=WKp-Q@mail.gmail.com/#t


Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      f333a3c7
  15. Jul 24, 2024
    • Joel Granados's avatar
      sysctl: treewide: constify the ctl_table argument of proc_handlers · 78eb4ea2
      Joel Granados authored 
      
const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.

This patch has been generated by the following coccinelle script:

```
  virtual patch

  @r1@
  identifier ctl, write, buffer, lenp, ppos;
  identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

  @r2@
  identifier func, ctl, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos)
  { ... }

  @r3@
  identifier func;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int , void *, size_t *, loff_t *);

  @r4@
  identifier func, ctl;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int , void *, size_t *, loff_t *);

  @r5@
  identifier func, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

```

* Code formatting was adjusted in xfs_sysctl.c to comply with code
  conventions. The xfs_stats_clear_proc_handler,
  xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
  adjusted.

* The ctl_table argument in proc_watchdog_common was const qualified.
  This is called from a proc_handler itself and is calling back into
  another proc_handler, making it necessary to change it as part of the
  proc_handler migration.

Co-developed-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Signed-off-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Co-developed-by: default avatarJoel Granados <j.granados@samsung.com>
Signed-off-by: default avatarJoel Granados <j.granados@samsung.com>
      78eb4ea2
    • Linus Torvalds's avatar
      hostfs: fix folio conversion · e44be002
      Linus Torvalds authored 
      Commit e3ec0fe9

 ("hostfs: Convert hostfs_read_folio() to use a
folio") simplified hostfs_read_folio(), but in the process of converting
to using folios natively also mis-used the folio_zero_tail() function
due to the very confusing API of that function.

Very arguably it's folio_zero_tail() API itself that is buggy, since it
would make more sense (and the documentation kind of implies) that the
third argument would be the pointer to the beginning of the folio
buffer.

But no, the third argument to folio_zero_tail() is where we should start
zeroing the tail (even if we already also pass in the offset separately
as the second argument).

So fix the hostfs caller, and we can leave any folio_zero_tail() sanity
cleanup for later.

Reported-and-tested-by: default avatarMaciej Żenczykowski <maze@google.com>
Fixes: e3ec0fe9 ("hostfs: Convert hostfs_read_folio() to use a folio")
Link: https://lore.kernel.org/all/CANP3RGceNzwdb7w=vPf5=7BCid5HVQDmz1K5kC9JG42+HVAh_g@mail.gmail.com/


Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e44be002
    • Christian Brauner's avatar
      inode: clarify what's locked · f5e5e97c
      Christian Brauner authored 
      
In __wait_on_freeing_inode() we warn in case the inode_hash_lock is held
but the inode is unhashed. We then release the inode_lock. So using
"locked" as parameter name is confusing. Use is_inode_hash_locked as
parameter name instead.

Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      f5e5e97c
    • David Howells's avatar
      vfs: Fix potential circular locking through setxattr() and removexattr() · c3a5e3e8
      David Howells authored 
      
When using cachefiles, lockdep may emit something similar to the circular
locking dependency notice below.  The problem appears to stem from the
following:

 (1) Cachefiles manipulates xattrs on the files in its cache when called
     from ->writepages().

 (2) The setxattr() and removexattr() system call handlers get the name
     (and value) from userspace after taking the sb_writers lock, putting
     accesses of the vma->vm_lock and mm->mmap_lock inside of that.

 (3) The afs filesystem uses a per-inode lock to prevent multiple
     revalidation RPCs and in writeback vs truncate to prevent parallel
     operations from deadlocking against the server on one side and local
     page locks on the other.

Fix this by moving the getting of the name and value in {get,remove}xattr()
outside of the sb_writers lock.  This also has the minor benefits that we
don't need to reget these in the event of a retry and we never try to take
the sb_writers lock in the event we can't pull the name and value into the
kernel.

Alternative approaches that might fix this include moving the dispatch of a
write to the cache off to a workqueue or trying to do without the
validation lock in afs.  Note that this might also affect other filesystems
that use netfslib and/or cachefiles.

 ======================================================
 WARNING: possible circular locking dependency detected
 6.10.0-build2+ #956 Not tainted
 ------------------------------------------------------
 fsstress/6050 is trying to acquire lock:
 ffff888138fd82f0 (mapping.invalidate_lock#3){++++}-{3:3}, at: filemap_fault+0x26e/0x8b0

 but task is already holding lock:
 ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #4 (&vma->vm_lock->lock){++++}-{3:3}:
        __lock_acquire+0xaf0/0xd80
        lock_acquire.part.0+0x103/0x280
        down_write+0x3b/0x50
        vma_start_write+0x6b/0xa0
        vma_link+0xcc/0x140
        insert_vm_struct+0xb7/0xf0
        alloc_bprm+0x2c1/0x390
        kernel_execve+0x65/0x1a0
        call_usermodehelper_exec_async+0x14d/0x190
        ret_from_fork+0x24/0x40
        ret_from_fork_asm+0x1a/0x30

 -> #3 (&mm->mmap_lock){++++}-{3:3}:
        __lock_acquire+0xaf0/0xd80
        lock_acquire.part.0+0x103/0x280
        __might_fault+0x7c/0xb0
        strncpy_from_user+0x25/0x160
        removexattr+0x7f/0x100
        __do_sys_fremovexattr+0x7e/0xb0
        do_syscall_64+0x9f/0x100
        entry_SYSCALL_64_after_hwframe+0x76/0x7e

 -> #2 (sb_writers#14){.+.+}-{0:0}:
        __lock_acquire+0xaf0/0xd80
        lock_acquire.part.0+0x103/0x280
        percpu_down_read+0x3c/0x90
        vfs_iocb_iter_write+0xe9/0x1d0
        __cachefiles_write+0x367/0x430
        cachefiles_issue_write+0x299/0x2f0
        netfs_advance_write+0x117/0x140
        netfs_write_folio.isra.0+0x5ca/0x6e0
        netfs_writepages+0x230/0x2f0
        afs_writepages+0x4d/0x70
        do_writepages+0x1e8/0x3e0
        filemap_fdatawrite_wbc+0x84/0xa0
        __filemap_fdatawrite_range+0xa8/0xf0
        file_write_and_wait_range+0x59/0x90
        afs_release+0x10f/0x270
        __fput+0x25f/0x3d0
        __do_sys_close+0x43/0x70
        do_syscall_64+0x9f/0x100
        entry_SYSCALL_64_after_hwframe+0x76/0x7e

 -> #1 (&vnode->validate_lock){++++}-{3:3}:
        __lock_acquire+0xaf0/0xd80
        lock_acquire.part.0+0x103/0x280
        down_read+0x95/0x200
        afs_writepages+0x37/0x70
        do_writepages+0x1e8/0x3e0
        filemap_fdatawrite_wbc+0x84/0xa0
        filemap_invalidate_inode+0x167/0x1e0
        netfs_unbuffered_write_iter+0x1bd/0x2d0
        vfs_write+0x22e/0x320
        ksys_write+0xbc/0x130
        do_syscall_64+0x9f/0x100
        entry_SYSCALL_64_after_hwframe+0x76/0x7e

 -> #0 (mapping.invalidate_lock#3){++++}-{3:3}:
        check_noncircular+0x119/0x160
        check_prev_add+0x195/0x430
        __lock_acquire+0xaf0/0xd80
        lock_acquire.part.0+0x103/0x280
        down_read+0x95/0x200
        filemap_fault+0x26e/0x8b0
        __do_fault+0x57/0xd0
        do_pte_missing+0x23b/0x320
        __handle_mm_fault+0x2d4/0x320
        handle_mm_fault+0x14f/0x260
        do_user_addr_fault+0x2a2/0x500
        exc_page_fault+0x71/0x90
        asm_exc_page_fault+0x22/0x30

 other info that might help us debug this:

 Chain exists of:
   mapping.invalidate_lock#3 --> &mm->mmap_lock --> &vma->vm_lock->lock

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   rlock(&vma->vm_lock->lock);
                                lock(&mm->mmap_lock);
                                lock(&vma->vm_lock->lock);
   rlock(mapping.invalidate_lock#3);

  *** DEADLOCK ***

 1 lock held by fsstress/6050:
  #0: ffff888113f26d18 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x165/0x250

 stack backtrace:
 CPU: 0 PID: 6050 Comm: fsstress Not tainted 6.10.0-build2+ #956
 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
 Call Trace:
  <TASK>
  dump_stack_lvl+0x57/0x80
  check_noncircular+0x119/0x160
  ? queued_spin_lock_slowpath+0x4be/0x510
  ? __pfx_check_noncircular+0x10/0x10
  ? __pfx_queued_spin_lock_slowpath+0x10/0x10
  ? mark_lock+0x47/0x160
  ? init_chain_block+0x9c/0xc0
  ? add_chain_block+0x84/0xf0
  check_prev_add+0x195/0x430
  __lock_acquire+0xaf0/0xd80
  ? __pfx___lock_acquire+0x10/0x10
  ? __lock_release.isra.0+0x13b/0x230
  lock_acquire.part.0+0x103/0x280
  ? filemap_fault+0x26e/0x8b0
  ? __pfx_lock_acquire.part.0+0x10/0x10
  ? rcu_is_watching+0x34/0x60
  ? lock_acquire+0xd7/0x120
  down_read+0x95/0x200
  ? filemap_fault+0x26e/0x8b0
  ? __pfx_down_read+0x10/0x10
  ? __filemap_get_folio+0x25/0x1a0
  filemap_fault+0x26e/0x8b0
  ? __pfx_filemap_fault+0x10/0x10
  ? find_held_lock+0x7c/0x90
  ? __pfx___lock_release.isra.0+0x10/0x10
  ? __pte_offset_map+0x99/0x110
  __do_fault+0x57/0xd0
  do_pte_missing+0x23b/0x320
  __handle_mm_fault+0x2d4/0x320
  ? __pfx___handle_mm_fault+0x10/0x10
  handle_mm_fault+0x14f/0x260
  do_user_addr_fault+0x2a2/0x500
  exc_page_fault+0x71/0x90
  asm_exc_page_fault+0x22/0x30

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/2136178.1721725194@warthog.procyon.org.uk


cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Christian Brauner <brauner@kernel.org>
cc: Jan Kara <jack@suse.cz>
cc: Jeff Layton <jlayton@kernel.org>
cc: Gao Xiang <xiang@kernel.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-erofs@lists.ozlabs.org
cc: linux-fsdevel@vger.kernel.org
[brauner: fix minor issues]
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      c3a5e3e8
    • Jann Horn's avatar
      filelock: Fix fcntl/close race recovery compat path · f8138f2a
      Jann Horn authored 
      When I wrote commit 3cad1bc0 ("filelock: Remove locks reliably when
fcntl/close race is detected"), I missed that there are two copies of the
code I was patching: The normal version, and the version for 64-bit offsets
on 32-bit kernels.
Thanks to Greg KH for stumbling over this while doing the stable
backport...

Apply exactly the same fix to the compat path for 32-bit kernels.

Fixes: c293621b ("[PATCH] stale POSIX lock handling")
Cc: stable@kernel.org
Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2563


Signed-off-by: default avatarJann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20240723-fs-lock-recover-compatfix-v1-1-148096719529@google.com


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      f8138f2a
    • Christian Brauner's avatar
      fs: use all available ids · 8eac5358
      Christian Brauner authored 
      The counter is unconditionally incremented for each mount allocation.
If we set it to 1ULL << 32 we're losing 4294967296 as the first valid
non-32 bit mount id.

Link: https://lore.kernel.org/r/20240719-work-mount-namespace-v1-1-834113cab0d2@kernel.org


Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      8eac5358
    • David Howells's avatar
      cachefiles: Set the max subreq size for cache writes to MAX_RW_COUNT · 51d37982
      David Howells authored 
      
Set the maximum size of a subrequest that writes to cachefiles to be
MAX_RW_COUNT so that we don't overrun the maximum write we can make to the
backing filesystem.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/1599005.1721398742@warthog.procyon.org.uk


cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      51d37982
    • David Howells's avatar
      netfs: Fix writeback that needs to go to both server and cache · 212be98a
      David Howells authored 
      When netfslib is performing writeback (ie. ->writepages), it maintains two
parallel streams of writes, one to the server and one to the cache, but it
doesn't mark either stream of writes as active until it gets some data that
needs to be written to that stream.

This is done because some folios will only be written to the cache
(e.g. copying to the cache on read is done by marking the folios and
letting writeback do the actual work) and sometimes we'll only be writing
to the server (e.g. if there's no cache).

Now, since we don't actually dispatch uploads and cache writes in parallel,
but rather flip between the streams, depending on which has the lowest
so-far-issued offset, and don't wait for the subreqs to finish before
flipping, we can end up in a situation where, say, we issue a write to the
server and this completes before we start the write to the cache.

But because we only activate a stream when we first add a subreq to it, the
result collection code may run before we manage to activate the stream -
resulting in the folio being cleaned and having the writeback-in-progress
mark removed.  At this point, the folio no longer belongs to us.

This is only really a problem for folios that need to be written to both
streams - and in that case, the upload to the server is started first,
followed by the write to the cache - and the cache write may see a bad
folio.

Fix this by activating the cache stream up front if there's a cache
available.  If there's a cache, then all data is going to be written to it.

Fixes: 288ace2f

 ("netfs: New writeback implementation")
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/1599053.1721398818@warthog.procyon.org.uk


cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      212be98a
    • Christian Brauner's avatar
      pidfs: handle kernels without namespaces cleanly · 9b3e1504
      Christian Brauner authored 
      The nsproxy structure contains nearly all of the namespaces associated
with a task. When a given namespace type is not supported by this kernel
the rules whether the corresponding pointer in struct nsproxy is NULL or
always init_<ns_type>_ns differ per namespace. Ideally, that wouldn't be
the case and for all namespace types we'd always set it to
init_<ns_type>_ns when the corresponding namespace type isn't supported.

Make sure we handle all namespaces where the pointer in struct nsproxy
can be NULL when the namespace type isn't supported.

Link: https://lore.kernel.org/r/20240722-work-pidfs-e6a83030f63e@brauner
Fixes: 5b08bd40

 ("pidfs: allow retrieval of namespace file descriptors") # mainline only
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      9b3e1504
    • Edward Adam Davis's avatar
      pidfs: when time ns disabled add check for ioctl · f60d38cb
      Edward Adam Davis authored 
      syzbot call pidfd_ioctl() with cmd "PIDFD_GET_TIME_NAMESPACE" and disabled
CONFIG_TIME_NS, since time_ns is NULL, it will make NULL ponter deref in
open_namespace.

Fixes: 5b08bd40

 ("pidfs: allow retrieval of namespace file descriptors") # mainline only
Reported-and-tested-by: default avatar <syzbot+34a0ee986f61f15da35d@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=34a0ee986f61f15da35d


Signed-off-by: default avatarEdward Adam Davis <eadavis@qq.com>
Link: https://lore.kernel.org/r/tencent_7FAE8DB725EE0DD69236DDABDDDE195E4F07@qq.com


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      f60d38cb
    • Congjie Zhou's avatar
      vfs: correct the comments of vfs_*() helpers · b40c8e7a
      Congjie Zhou authored 
      correct the comments of vfs_*() helpers in fs/namei.c, including:
1. vfs_create()
2. vfs_mknod()
3. vfs_mkdir()
4. vfs_rmdir()
5. vfs_symlink()

All of them come from the same commit:
6521f891

 "namei: prepare for idmapped mounts"

The @dentry is actually the dentry of child directory rather than
base directory(parent directory), and thus the @dir has to be
modified due to the change of @dentry.

Signed-off-by: default avatarCongjie Zhou <zcjie0802@qq.com>
Link: https://lore.kernel.org/r/tencent_2FCF6CC9E10DC8A27AE58A5A0FE4FCE96D0A@qq.com


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      b40c8e7a
    • Mateusz Guzik's avatar
      vfs: handle __wait_on_freeing_inode() and evict() race · 5bc9ad78
      Mateusz Guzik authored 
      Lockless hash lookup can find and lock the inode after it gets the
I_FREEING flag set, at which point it blocks waiting for teardown in
evict() to finish.

However, the flag is still set even after evict() wakes up all waiters.

This results in a race where if the inode lock is taken late enough, it
can happen after both hash removal and wakeups, meaning there is nobody
to wake the racing thread up.

This worked prior to RCU-based lookup because the entire ordeal was
synchronized with the inode hash lock.

Since unhashing requires the inode lock, we can safely check whether it
happened after acquiring it.

Link: https://lore.kernel.org/v9fs/20240717102458.649b60be@kernel.org/


Reported-by: default avatarDominique Martinet <asmadeus@codewreck.org>
Fixes: 7180f8d9

 ("vfs: add rcu-based find_inode variants for iget ops")
Signed-off-by: default avatarMateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/r/20240718151838.611807-1-mjguzik@gmail.com


Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      5bc9ad78
    • David Howells's avatar
      netfs: Rename CONFIG_FSCACHE_DEBUG to CONFIG_NETFS_DEBUG · fcad9336
      David Howells authored 
      
CONFIG_FSCACHE_DEBUG should have been renamed to CONFIG_NETFS_DEBUG, so do
that now.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/1410796.1721333406@warthog.procyon.org.uk


cc: Uwe Kleine-König <ukleinek@kernel.org>
cc: Christian Brauner <brauner@kernel.org>
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
      fcad9336

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