6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Howells dhowells@redhat.com
[ Upstream commit 4481f7f2b3df123ec77e828c849138f75cff2bf2 ]
Fix the resetting of the subrequest iterator in netfs_retry_write_stream() to use the iterator-reset function as the iterator may have been shortened by a previous retry. In such a case, the amount of data to be written by the subrequest is not "subreq->len" but "subreq->len - subreq->transferred".
Without this, KASAN may see an error in iov_iter_revert():
BUG: KASAN: slab-out-of-bounds in iov_iter_revert lib/iov_iter.c:633 [inline] BUG: KASAN: slab-out-of-bounds in iov_iter_revert+0x443/0x5a0 lib/iov_iter.c:611 Read of size 4 at addr ffff88802912a0b8 by task kworker/u32:7/1147
CPU: 1 UID: 0 PID: 1147 Comm: kworker/u32:7 Not tainted 6.15.0-rc6-syzkaller-00052-g9f35e33144ae #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Workqueue: events_unbound netfs_write_collection_worker Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xc3/0x670 mm/kasan/report.c:521 kasan_report+0xe0/0x110 mm/kasan/report.c:634 iov_iter_revert lib/iov_iter.c:633 [inline] iov_iter_revert+0x443/0x5a0 lib/iov_iter.c:611 netfs_retry_write_stream fs/netfs/write_retry.c:44 [inline] netfs_retry_writes+0x166d/0x1a50 fs/netfs/write_retry.c:231 netfs_collect_write_results fs/netfs/write_collect.c:352 [inline] netfs_write_collection_worker+0x23fd/0x3830 fs/netfs/write_collect.c:374 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238 process_scheduled_works kernel/workqueue.c:3319 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400 kthread+0x3c2/0x780 kernel/kthread.c:464 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK>
Fixes: cd0277ed0c18 ("netfs: Use new folio_queue data type and iterator instead of xarray iter") Reported-by: syzbot+25b83a6f2c702075fcbc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=25b83a6f2c702075fcbc Signed-off-by: David Howells dhowells@redhat.com Link: https://lore.kernel.org/20250519090707.2848510-2-dhowells@redhat.com Tested-by: syzbot+25b83a6f2c702075fcbc@syzkaller.appspotmail.com cc: Paulo Alcantara pc@manguebit.com cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/netfs/write_collect.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/netfs/write_collect.c b/fs/netfs/write_collect.c index 412d4da742270..7cb21da40a0a4 100644 --- a/fs/netfs/write_collect.c +++ b/fs/netfs/write_collect.c @@ -176,9 +176,10 @@ static void netfs_retry_write_stream(struct netfs_io_request *wreq, if (test_bit(NETFS_SREQ_FAILED, &subreq->flags)) break; if (__test_and_clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) { - struct iov_iter source = subreq->io_iter; + struct iov_iter source;
- iov_iter_revert(&source, subreq->len - source.count); + netfs_reset_iter(subreq); + source = subreq->io_iter; __set_bit(NETFS_SREQ_RETRYING, &subreq->flags); netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit); netfs_reissue_write(stream, subreq, &source);