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author | Stefan Metzmacher <metze@samba.org> | 2022-09-29 09:39:10 +0200 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2022-09-29 15:08:21 +0200 |
commit | 3e4cb6ebbb2bad201c1186bc0b7e8cf41dd7f7e6 (patch) | |
tree | 5ef17238940a26a1c2766440072aba3841c5afec /io_uring/net.c | |
parent | io_uring/net: fix non-zc send with address (diff) | |
download | linux-3e4cb6ebbb2bad201c1186bc0b7e8cf41dd7f7e6.tar.xz linux-3e4cb6ebbb2bad201c1186bc0b7e8cf41dd7f7e6.zip |
io_uring/net: fix fast_iov assignment in io_setup_async_msg()
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>
Diffstat (limited to 'io_uring/net.c')
-rw-r--r-- | io_uring/net.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/io_uring/net.c b/io_uring/net.c index 23922365f08f..9ada9da02d04 100644 --- a/io_uring/net.c +++ b/io_uring/net.c @@ -166,8 +166,10 @@ static int io_setup_async_msg(struct io_kiocb *req, memcpy(async_msg, kmsg, sizeof(*kmsg)); async_msg->msg.msg_name = &async_msg->addr; /* if were using fast_iov, set it to the new one */ - if (!async_msg->free_iov) - async_msg->msg.msg_iter.iov = async_msg->fast_iov; + if (!kmsg->free_iov) { + size_t fast_idx = kmsg->msg.msg_iter.iov - kmsg->fast_iov; + async_msg->msg.msg_iter.iov = &async_msg->fast_iov[fast_idx]; + } return -EAGAIN; } |