* [PATCH] net: kcm: use previously opened message only once
@ 2024-08-01 13:08 Dmitry Antipov
2024-08-06 0:00 ` Jakub Kicinski
0 siblings, 1 reply; 2+ messages in thread
From: Dmitry Antipov @ 2024-08-01 13:08 UTC (permalink / raw)
To: Tom Herbert
Cc: Jakub Kicinski, Paolo Abeni, netdev, lvc-project, Dmitry Antipov,
syzbot+b72d86aa5df17ce74c60
When syzkaller reproducer injects 'alloc_skb()' failure at line
817, 'kcm_sendmsg()' may return with partial message saved at
'kcm->seq_skb'. Next call of this function will try to build the
next message starting from the saved one, but should do it only
once. Otherwise a complete mess in skb management causes an
undefined behavior of any kind, including UAFs reported by KASAN.
Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
Reported-by: syzbot+b72d86aa5df17ce74c60@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b72d86aa5df17ce74c60
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
---
net/kcm/kcmsock.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 2f191e50d4fc..fa5ce5c88045 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -766,6 +766,8 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
if (kcm->seq_skb) {
/* Previously opened message */
head = kcm->seq_skb;
+ /* ...should be used only once */
+ kcm->seq_skb = NULL;
skb = kcm_tx_msg(head)->last_skb;
goto start;
}
--
2.45.2
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] net: kcm: use previously opened message only once
2024-08-01 13:08 [PATCH] net: kcm: use previously opened message only once Dmitry Antipov
@ 2024-08-06 0:00 ` Jakub Kicinski
0 siblings, 0 replies; 2+ messages in thread
From: Jakub Kicinski @ 2024-08-06 0:00 UTC (permalink / raw)
To: Dmitry Antipov
Cc: Tom Herbert, Paolo Abeni, netdev, lvc-project,
syzbot+b72d86aa5df17ce74c60
On Thu, 1 Aug 2024 16:08:33 +0300 Dmitry Antipov wrote:
> When syzkaller reproducer injects 'alloc_skb()' failure at line
> 817, 'kcm_sendmsg()' may return with partial message saved at
> 'kcm->seq_skb'. Next call of this function will try to build the
> next message starting from the saved one, but should do it only
> once. Otherwise a complete mess in skb management causes an
> undefined behavior of any kind, including UAFs reported by KASAN.
>
> Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
> Reported-by: syzbot+b72d86aa5df17ce74c60@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=b72d86aa5df17ce74c60
> Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
> ---
> net/kcm/kcmsock.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
> index 2f191e50d4fc..fa5ce5c88045 100644
> --- a/net/kcm/kcmsock.c
> +++ b/net/kcm/kcmsock.c
> @@ -766,6 +766,8 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
> if (kcm->seq_skb) {
> /* Previously opened message */
> head = kcm->seq_skb;
> + /* ...should be used only once */
> + kcm->seq_skb = NULL;
> skb = kcm_tx_msg(head)->last_skb;
> goto start;
> }
Not sure how much this matters but if we clear seq_skb then handling
here:
https://elixir.bootlin.com/linux/v6.10-rc4/source/net/kcm/kcmsock.c#L940
will work differently.
^ permalink raw reply [flat|nested] 2+ messages in thread
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