On 11/3/21 17:01, Lee Jones wrote:
Good afternoon Pavel,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-and-tested-by: syzbot+9671693590ef5aad8953@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested on:
commit: bff2c168 io_uring: don't retry with truncated iter
git tree: https://github.com/isilence/linux.git truncate
kernel config: https://syzkaller.appspot.com/x/.config?x=730106bfb5bf8ace
dashboard link: https://syzkaller.appspot.com/bug?extid=9671693590ef5aad8953
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
Note: testing is done by a robot and is best-effort only.
As you can see in the 'dashboard link' above this bug also affects
android-5-10 which is currently based on v5.10.75.
I see that the back-port of this patch failed in v5.10.y:
https://lore.kernel.org/stable/163152589512611@xxxxxxxxx/
And after solving the build-error by back-porting both:
2112ff5ce0c11 iov_iter: track truncated size
89c2b3b749182 io_uring: reexpand under-reexpanded iters
I now see execution tripping the WARN() in iov_iter_revert():
if (WARN_ON(unroll > MAX_RW_COUNT))
return
Am I missing any additional patches required to fix stable/v5.10.y?
Is it the same syz test? There was a couple more patches for
IORING_SETUP_IOPOLL, but strange if that's not the case.
fwiw, Jens decided to replace it with another mechanism shortly
after, so it may be a better idea to backport those. Jens,
what do you think?
commit 8fb0f47a9d7acf620d0fd97831b69da9bc5e22ed
Author: Jens Axboe <axboe@xxxxxxxxx>
Date: Fri Sep 10 11:18:36 2021 -0600
iov_iter: add helper to save iov_iter state
commit cd65869512ab5668a5d16f789bc4da1319c435c4
Author: Jens Axboe <axboe@xxxxxxxxx>
Date: Fri Sep 10 11:19:14 2021 -0600
io_uring: use iov_iter state save/restore helpers
--
Pavel Begunkov
