github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-07 06:17:02 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

splice: avoid stale f_pos writeback on error

Browse Source 
do_splice() snapshots an implicit file position before calling the splice
helper. Since splice does not take f_pos_lock, another operation on the
same open file description can update f_pos while the helper is blocked.
If the helper then fails, the unconditional writeback restores the stale
snapshot.

For a directory without ->splice_read, a file-to-pipe splice fails with
-EINVAL. A concurrent directory mutation and getdents() call can advance
f_pos and refresh the filesystem's revalidation cookie before that failure
restores only the old position. The next ext2 readdir can then trust an
offset inside a directory entry and copy data from the adjacent page to
userspace.

Only update an implicit file position when splice returns a non-negative
result, matching read and write. Keep explicit offset updates unchanged.

Fixes: 7995bd2871 ("splice: don't pass the address of ->f_pos to methods")
Cc: stable@vger.kernel.org
Signed-off-by: Daehyeon Ko <4ncienth@gmail.com>
Link: https://patch.msgid.link/20261018051708.2422394-1-4ncienth@gmail.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Daehyeon Ko 2026-10-18 14:17:08 +09:00 committed by Christian Brauner
parent 627cdcbc2a
commit 79b496ebe3
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
fs/splice.c
View File

@ -1377,10 +1377,10 @@ ssize_t do_splice(struct file *in, loff_t *off_in, struct file *out,
ret = do_splice_from(ipipe, out, &offset, len, flags);
file_end_write(out);
if (!off_out)
out->f_pos = offset;
else
if (off_out)
*off_out = offset;
else if (ret >= 0)
out->f_pos = offset;
} else if (opipe) {
if (off_out)
return -ESPIPE;
@ -1401,10 +1401,10 @@ ssize_t do_splice(struct file *in, loff_t *off_in, struct file *out,
ret = splice_file_to_pipe(in, opipe, &offset, len, flags);
if (!off_in)
in->f_pos = offset;
else
if (off_in)
*off_in = offset;
else if (ret >= 0)
in->f_pos = offset;
} else {
ret = -EINVAL;
}