tree 9d38220e5133a7792620740ac4a99b9f2ce40fd0
parent 207ce626add80ddd941f62fc2fe5d77586e0801b
author Tung Nguyen <tung.q.nguyen@dektech.com.au> 1676337966 +0000
committer Jakub Kicinski <kuba@kernel.org> 1676436384 -0800

tipc: fix kernel warning when sending SYN message

When sending a SYN message, this kernel stack trace is observed:

...
[   13.396352] RIP: 0010:_copy_from_iter+0xb4/0x550
...
[   13.398494] Call Trace:
[   13.398630]  <TASK>
[   13.398630]  ? __alloc_skb+0xed/0x1a0
[   13.398630]  tipc_msg_build+0x12c/0x670 [tipc]
[   13.398630]  ? shmem_add_to_page_cache.isra.71+0x151/0x290
[   13.398630]  __tipc_sendmsg+0x2d1/0x710 [tipc]
[   13.398630]  ? tipc_connect+0x1d9/0x230 [tipc]
[   13.398630]  ? __local_bh_enable_ip+0x37/0x80
[   13.398630]  tipc_connect+0x1d9/0x230 [tipc]
[   13.398630]  ? __sys_connect+0x9f/0xd0
[   13.398630]  __sys_connect+0x9f/0xd0
[   13.398630]  ? preempt_count_add+0x4d/0xa0
[   13.398630]  ? fpregs_assert_state_consistent+0x22/0x50
[   13.398630]  __x64_sys_connect+0x16/0x20
[   13.398630]  do_syscall_64+0x42/0x90
[   13.398630]  entry_SYSCALL_64_after_hwframe+0x63/0xcd

It is because commit a41dad905e5a ("iov_iter: saner checks for attempt
to copy to/from iterator") has introduced sanity check for copying
from/to iov iterator. Lacking of copy direction from the iterator
viewpoint would lead to kernel stack trace like above.

This commit fixes this issue by initializing the iov iterator with
the correct copy direction when sending SYN or ACK without data.

Fixes: f25dcc7687d4 ("tipc: tipc ->sendmsg() conversion")
Reported-by: syzbot+d43608d061e8847ec9f3@syzkaller.appspotmail.com
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>
Link: https://lore.kernel.org/r/20230214012606.5804-1-tung.q.nguyen@dektech.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>