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Message-ID: <b36e496792de3d1811ea38f19588e5a5b32a9d2c.camel@redhat.com>
Date: Thu, 09 Feb 2023 11:38:46 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Tung Nguyen <tung.q.nguyen@...tech.com.au>, netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
jmaloy@...hat.com, ying.xue@...driver.com, viro@...iv.linux.org.uk,
syzbot+d43608d061e8847ec9f3@...kaller.appspotmail.com
Subject: Re: [PATCH v2 net 1/1] tipc: fix kernel warning when sending SYN
message
On Wed, 2023-02-08 at 07:07 +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.
>
> This commit fixes this issue by initializing the iov iterator with
> the correct copy direction.
>
> Fixes: f25dcc7687d4 ("tipc: tipc ->sendmsg() conversion")
> Reported-by: syzbot+d43608d061e8847ec9f3@...kaller.appspotmail.com
> Acked-by: Jon Maloy <jmaloy@...hat.com>
> Signed-off-by: Tung Nguyen <tung.q.nguyen@...tech.com.au>
> ---
> v2: add Fixes tag
>
> net/tipc/msg.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/tipc/msg.c b/net/tipc/msg.c
> index 5c9fd4791c4b..cce118fea07a 100644
> --- a/net/tipc/msg.c
> +++ b/net/tipc/msg.c
> @@ -381,6 +381,9 @@ int tipc_msg_build(struct tipc_msg *mhdr, struct msghdr *m, int offset,
>
> msg_set_size(mhdr, msz);
>
> + if (!dsz)
> + iov_iter_init(&m->msg_iter, ITER_SOURCE, NULL, 0, 0);
It looks like the root cause of the problem is that not all (indirect)
callers of tipc_msg_build() properly initialize the iter.
tipc_connect() is one of such caller, but AFAICS even tipc_accept() can
reach tipc_msg_build() without proper iter initialization - via
__tipc_sendstream -> __tipc_sendmsg.
I think it's better if you address the issue in relevant callers,
avoiding unneeded and confusing code in tipc_msg_build().
Thanks,
Paolo
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