From 14b1cd25346b1d615616a9c2dfdad9b4e6581e0d Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Mon, 13 May 2024 17:02:05 -0500
Subject: [PATCH] cifs: Fix locking in cifs_strict_readv()
Fix to take the i_rwsem (through the netfs locking wrappers) before taking
cinode->lock_sem.
Fixes: 3ee1a1fc3981 ("cifs: Cut over to using netfslib")
Reported-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
fs/netfs/direct_read.c | 3 ++-
fs/smb/client/cifsglob.h | 1 +
fs/smb/client/file.c | 34 +++++++++++++++++++++++++---------
include/linux/netfs.h | 1 +
4 files changed, 29 insertions(+), 10 deletions(-)
diff --git a/fs/netfs/direct_read.c b/fs/netfs/direct_read.c
index ad4370b3935d6..10a1e4da6bda5 100644
--- a/fs/netfs/direct_read.c
+++ b/fs/netfs/direct_read.c
@@ -26,7 +26,7 @@
*
* The caller must hold any appropriate locks.
*/
-static ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter)
+ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter)
{
struct netfs_io_request *rreq;
ssize_t ret;
@@ -98,6 +98,7 @@ static ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_
iov_iter_revert(iter, orig_count - iov_iter_count(iter));
return ret;
}
+EXPORT_SYMBOL(netfs_unbuffered_read_iter_locked);
/**
* netfs_unbuffered_read_iter - Perform an unbuffered or direct I/O read
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 65574e69ba4f9..73482734a8d8e 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1995,6 +1995,7 @@ require use of the stronger protocol */
* ->chans_need_reconnect
* ->chans_in_reconnect
* cifs_tcon->tc_lock (anything that is not protected by another lock and can change)
+ * inode->i_rwsem, taken by fs/netfs/locking.c e.g. should be taken before cifsInodeInfo locks
* cifsInodeInfo->open_file_lock cifsInodeInfo->openFileList cifs_alloc_inode
* cifsInodeInfo->writers_lock cifsInodeInfo->writers cifsInodeInfo_alloc
* cifsInodeInfo->lock_sem cifsInodeInfo->llist cifs_init_once
diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index 4c981ce89f8a7..9d38294a7e680 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -2916,16 +2916,32 @@ cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to)
* We need to hold the sem to be sure nobody modifies lock list
* with a brlock that prevents reading.
*/
- down_read(&cinode->lock_sem);
- if (!cifs_find_lock_conflict(cfile, iocb->ki_pos, iov_iter_count(to),
- tcon->ses->server->vals->shared_lock_type,
- 0, NULL, CIFS_READ_OP)) {
- if (iocb->ki_flags & IOCB_DIRECT)
- rc = netfs_unbuffered_read_iter(iocb, to);
- else
- rc = netfs_buffered_read_iter(iocb, to);
+ if (iocb->ki_flags & IOCB_DIRECT) {
+ rc = netfs_start_io_direct(inode);
+ if (rc < 0)
+ goto out;
+ down_read(&cinode->lock_sem);
+ if (!cifs_find_lock_conflict(
+ cfile, iocb->ki_pos, iov_iter_count(to),
+ tcon->ses->server->vals->shared_lock_type,
+ 0, NULL, CIFS_READ_OP))
+ rc = netfs_unbuffered_read_iter_locked(iocb, to);
+ up_read(&cinode->lock_sem);
+ netfs_end_io_direct(inode);
+ } else {
+ rc = netfs_start_io_read(inode);
+ if (rc < 0)
+ goto out;
+ down_read(&cinode->lock_sem);
+ if (!cifs_find_lock_conflict(
+ cfile, iocb->ki_pos, iov_iter_count(to),
+ tcon->ses->server->vals->shared_lock_type,
+ 0, NULL, CIFS_READ_OP))
+ rc = filemap_read(iocb, to, 0);
+ up_read(&cinode->lock_sem);
+ netfs_end_io_read(inode);
}
- up_read(&cinode->lock_sem);
+out:
return rc;
}
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index f45d06284f2f8..ca56a4428043d 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -389,6 +389,7 @@ struct netfs_cache_ops {
};
/* High-level read API. */
+ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter);
--
GitLab