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| author | Deepanshu Kartikey <kartikey406@gmail.com> | 2026-03-07 10:09:47 +0530 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2026-03-09 10:21:56 +0100 |
| commit | e9075e420a1eb3b52c60f3b95893a55e77419ce8 (patch) | |
| tree | ae0861e4d1aa617f30e946639c028750cbf7d6d1 /fs/netfs | |
| parent | 67e467a11f62ff64ad219dc6aa5459e132c79d14 (diff) | |
| download | linux-next-e9075e420a1eb3b52c60f3b95893a55e77419ce8.tar.gz linux-next-e9075e420a1eb3b52c60f3b95893a55e77419ce8.zip | |
netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry
When a write subrequest is marked NETFS_SREQ_NEED_RETRY, the retry path
in netfs_unbuffered_write() unconditionally calls stream->prepare_write()
without checking if it is NULL.
Filesystems such as 9P do not set the prepare_write operation, so
stream->prepare_write remains NULL. When get_user_pages() fails with
-EFAULT and the subrequest is flagged for retry, this results in a NULL
pointer dereference at fs/netfs/direct_write.c:189.
Fix this by mirroring the pattern already used in write_retry.c: if
stream->prepare_write is NULL, skip renegotiation and directly reissue
the subrequest via netfs_reissue_write(), which handles iterator reset,
IN_PROGRESS flag, stats update and reissue internally.
Fixes: a0b4c7a49137 ("netfs: Fix unbuffered/DIO writes to dispatch subrequests in strict sequence")
Reported-by: syzbot+7227db0fbac9f348dba0@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7227db0fbac9f348dba0
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
Link: https://patch.msgid.link/20260307043947.347092-1-kartikey406@gmail.com
Tested-by: syzbot+7227db0fbac9f348dba0@syzkaller.appspotmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/netfs')
| -rw-r--r-- | fs/netfs/direct_write.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c index dd1451bf7543..4d9760e36c11 100644 --- a/fs/netfs/direct_write.c +++ b/fs/netfs/direct_write.c @@ -186,10 +186,18 @@ static int netfs_unbuffered_write(struct netfs_io_request *wreq) stream->sreq_max_segs = INT_MAX; netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit); - stream->prepare_write(subreq); - __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags); - netfs_stat(&netfs_n_wh_retry_write_subreq); + if (stream->prepare_write) { + stream->prepare_write(subreq); + __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags); + netfs_stat(&netfs_n_wh_retry_write_subreq); + } else { + struct iov_iter source; + + netfs_reset_iter(subreq); + source = subreq->io_iter; + netfs_reissue_write(stream, subreq, &source); + } } netfs_unbuffered_write_done(wreq); |