Re: [PATCH net 1/1] tipc: fix kernel warning when sending SYN message

[Jakub Kicinski <kuba@kernel.org>]

On Tue,  7 Feb 2023 01:20:46 +0000 Tung Nguyen wrote:
> 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.

How far does the bug itself date, tho?
Can we get a Fixes tag?

> This commit fixes this issue by initializing the iov iterator with
> the correct copy direction.