From 4f526fef91b24197d489ff86789744c67f475bb4 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Mon, 3 Oct 2022 20:26:08 -0400
Subject: [PATCH] [brown paperbag] fix coredump breakage
Let me count the ways in which I'd screwed up:
* when emitting a page, handling of gaps in coredump should happen
before fetching the current file position.
* fix for a problem that occurs on rather uncommon setups (and hadn't
been observed in the wild) had been sent very late in the cycle.
* ... with badly insufficient testing, introducing an easily
reproducible breakage. Without giving it time to soak in -next.
Fucked-up-by: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: "J. R. Okajima" <hooanon05g@gmail.com>
Tested-by: "J. R. Okajima" <hooanon05g@gmail.com>
Fixes: 06bbaa6dc53c "[coredump] don't use __kernel_write() on kmap_local_page()"
Cc: stable@kernel.org # v6.0-only
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/coredump.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/coredump.c b/fs/coredump.c
index 1ab4f5b76a1e7..3538f3a63965d 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -841,7 +841,7 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
};
struct iov_iter iter;
struct file *file = cprm->file;
- loff_t pos = file->f_pos;
+ loff_t pos;
ssize_t n;
if (cprm->to_skip) {
@@ -853,6 +853,7 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
return 0;
if (dump_interrupted())
return 0;
+ pos = file->f_pos;
iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE);
n = __kernel_write_iter(cprm->file, &iter, &pos);
if (n != PAGE_SIZE)
--
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