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author | Stefan Metzmacher <metze@samba.org> | 2022-09-29 10:39:10 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-01-24 09:20:01 +0300 |
commit | fc2491562a9bed1f3e58a8ebdd4176962640e58c (patch) | |
tree | 18ea3178c0d23725849043ccef6fe161a5974d1e /net | |
parent | 89a77271d254752d83507fc347dc2d675885fe07 (diff) | |
download | linux-fc2491562a9bed1f3e58a8ebdd4176962640e58c.tar.xz |
io_uring/net: fix fast_iov assignment in io_setup_async_msg()
commit 3e4cb6ebbb2bad201c1186bc0b7e8cf41dd7f7e6 upstream.
I hit a very bad problem during my tests of SENDMSG_ZC.
BUG(); in first_iovec_segment() triggered very easily.
The problem was io_setup_async_msg() in the partial retry case,
which seems to happen more often with _ZC.
iov_iter_iovec_advance() may change i->iov in order to have i->iov_offset
being only relative to the first element.
Which means kmsg->msg.msg_iter.iov is no longer the
same as kmsg->fast_iov.
But this would rewind the copy to be the start of
async_msg->fast_iov, which means the internal
state of sync_msg->msg.msg_iter is inconsitent.
I tested with 5 vectors with length like this 4, 0, 64, 20, 8388608
and got a short writes with:
- ret=2675244 min_ret=8388692 => remaining 5713448 sr->done_io=2675244
- ret=-EAGAIN => io_uring_poll_arm
- ret=4911225 min_ret=5713448 => remaining 802223 sr->done_io=7586469
- ret=-EAGAIN => io_uring_poll_arm
- ret=802223 min_ret=802223 => res=8388692
While this was easily triggered with SENDMSG_ZC (queued for 6.1),
it was a potential problem starting with 7ba89d2af17aa879dda30f5d5d3f152e587fc551
in 5.18 for IORING_OP_RECVMSG.
And also with 4c3c09439c08b03d9503df0ca4c7619c5842892e in 5.19
for IORING_OP_SENDMSG.
However 257e84a5377fbbc336ff563833a8712619acce56 introduced the critical
code into io_setup_async_msg() in 5.11.
Fixes: 7ba89d2af17aa ("io_uring: ensure recv and recvmsg handle MSG_WAITALL correctly")
Fixes: 257e84a5377fb ("io_uring: refactor sendmsg/recvmsg iov managing")
Cc: stable@vger.kernel.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b2e7be246e2fb173520862b0c7098e55767567a2.1664436949.git.metze@samba.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
0 files changed, 0 insertions, 0 deletions