* [PATCH net] kcm: avoid potential race in kcm_tx_work
@ 2022-10-12 13:34 Eric Dumazet
2022-10-12 14:00 ` Dmitry Vyukov
2022-10-13 16:50 ` patchwork-bot+netdevbpf
0 siblings, 2 replies; 4+ messages in thread
From: Eric Dumazet @ 2022-10-12 13:34 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: netdev, eric.dumazet, Eric Dumazet, syzbot, Tom Herbert
syzbot found that kcm_tx_work() could crash [1] in:
/* Primarily for SOCK_SEQPACKET sockets */
if (likely(sk->sk_socket) &&
test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
<<*>> clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
sk->sk_write_space(sk);
}
I think the reason is that another thread might concurrently
run in kcm_release() and call sock_orphan(sk) while sk is not
locked. kcm_tx_work() find sk->sk_socket being NULL.
[1]
BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:86 [inline]
BUG: KASAN: null-ptr-deref in clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
BUG: KASAN: null-ptr-deref in kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742
Write of size 8 at addr 0000000000000008 by task kworker/u4:3/53
CPU: 0 PID: 53 Comm: kworker/u4:3 Not tainted 5.19.0-rc3-next-20220621-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kkcmd kcm_tx_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
kasan_report+0xbe/0x1f0 mm/kasan/report.c:495
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
instrument_atomic_write include/linux/instrumented.h:86 [inline]
clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742
process_one_work+0x996/0x1610 kernel/workqueue.c:2289
worker_thread+0x665/0x1080 kernel/workqueue.c:2436
kthread+0x2e9/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302
</TASK>
Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <tom@herbertland.com>
---
net/kcm/kcmsock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 1215c863e1c410fa9ba5b9c3706152decfb3ebac..27725464ec08fe2b5f2e86202636cbc895568098 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1838,10 +1838,10 @@ static int kcm_release(struct socket *sock)
kcm = kcm_sk(sk);
mux = kcm->mux;
+ lock_sock(sk);
sock_orphan(sk);
kfree_skb(kcm->seq_skb);
- lock_sock(sk);
/* Purge queue under lock to avoid race condition with tx_work trying
* to act when queue is nonempty. If tx_work runs after this point
* it will just return.
--
2.38.0.rc1.362.ged0d419d3c-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH net] kcm: avoid potential race in kcm_tx_work
2022-10-12 13:34 [PATCH net] kcm: avoid potential race in kcm_tx_work Eric Dumazet
@ 2022-10-12 14:00 ` Dmitry Vyukov
2022-10-12 14:38 ` Eric Dumazet
2022-10-13 16:50 ` patchwork-bot+netdevbpf
1 sibling, 1 reply; 4+ messages in thread
From: Dmitry Vyukov @ 2022-10-12 14:00 UTC (permalink / raw)
To: Eric Dumazet
Cc: David S . Miller, Jakub Kicinski, Paolo Abeni, netdev,
eric.dumazet, syzbot, Tom Herbert
On Wed, 12 Oct 2022 at 15:34, 'Eric Dumazet' via syzkaller
<syzkaller@googlegroups.com> wrote:
>
> syzbot found that kcm_tx_work() could crash [1] in:
>
> /* Primarily for SOCK_SEQPACKET sockets */
> if (likely(sk->sk_socket) &&
> test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
> <<*>> clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
> sk->sk_write_space(sk);
> }
>
> I think the reason is that another thread might concurrently
> run in kcm_release() and call sock_orphan(sk) while sk is not
> locked. kcm_tx_work() find sk->sk_socket being NULL.
Does it make sense to add some lockdep annotations to sock_orphan()
and maybe some other similar functions to catch such cases earlier?
> [1]
> BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:86 [inline]
> BUG: KASAN: null-ptr-deref in clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
> BUG: KASAN: null-ptr-deref in kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742
> Write of size 8 at addr 0000000000000008 by task kworker/u4:3/53
>
> CPU: 0 PID: 53 Comm: kworker/u4:3 Not tainted 5.19.0-rc3-next-20220621-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Workqueue: kkcmd kcm_tx_work
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> kasan_report+0xbe/0x1f0 mm/kasan/report.c:495
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> instrument_atomic_write include/linux/instrumented.h:86 [inline]
> clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
> kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742
> process_one_work+0x996/0x1610 kernel/workqueue.c:2289
> worker_thread+0x665/0x1080 kernel/workqueue.c:2436
> kthread+0x2e9/0x3a0 kernel/kthread.c:376
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302
> </TASK>
>
> Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Tom Herbert <tom@herbertland.com>
> ---
> net/kcm/kcmsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
> index 1215c863e1c410fa9ba5b9c3706152decfb3ebac..27725464ec08fe2b5f2e86202636cbc895568098 100644
> --- a/net/kcm/kcmsock.c
> +++ b/net/kcm/kcmsock.c
> @@ -1838,10 +1838,10 @@ static int kcm_release(struct socket *sock)
> kcm = kcm_sk(sk);
> mux = kcm->mux;
>
> + lock_sock(sk);
> sock_orphan(sk);
> kfree_skb(kcm->seq_skb);
>
> - lock_sock(sk);
> /* Purge queue under lock to avoid race condition with tx_work trying
> * to act when queue is nonempty. If tx_work runs after this point
> * it will just return.
> --
> 2.38.0.rc1.362.ged0d419d3c-goog
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller/20221012133412.519394-1-edumazet%40google.com.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] kcm: avoid potential race in kcm_tx_work
2022-10-12 14:00 ` Dmitry Vyukov
@ 2022-10-12 14:38 ` Eric Dumazet
0 siblings, 0 replies; 4+ messages in thread
From: Eric Dumazet @ 2022-10-12 14:38 UTC (permalink / raw)
To: Dmitry Vyukov
Cc: David S . Miller, Jakub Kicinski, Paolo Abeni, netdev,
eric.dumazet, syzbot, Tom Herbert
On Wed, Oct 12, 2022 at 7:00 AM Dmitry Vyukov <dvyukov@google.com> wrote:
>
> On Wed, 12 Oct 2022 at 15:34, 'Eric Dumazet' via syzkaller
> <syzkaller@googlegroups.com> wrote:
> >
> > syzbot found that kcm_tx_work() could crash [1] in:
> >
> > /* Primarily for SOCK_SEQPACKET sockets */
> > if (likely(sk->sk_socket) &&
> > test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
> > <<*>> clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
> > sk->sk_write_space(sk);
> > }
> >
> > I think the reason is that another thread might concurrently
> > run in kcm_release() and call sock_orphan(sk) while sk is not
> > locked. kcm_tx_work() find sk->sk_socket being NULL.
>
> Does it make sense to add some lockdep annotations to sock_orphan()
> and maybe some other similar functions to catch such cases earlier?
I thought about that, but this seems net-next material.
>
>
> > [1]
> > BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:86 [inline]
> > BUG: KASAN: null-ptr-deref in clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
> > BUG: KASAN: null-ptr-deref in kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742
> > Write of size 8 at addr 0000000000000008 by task kworker/u4:3/53
> >
> > CPU: 0 PID: 53 Comm: kworker/u4:3 Not tainted 5.19.0-rc3-next-20220621-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Workqueue: kkcmd kcm_tx_work
> > Call Trace:
> > <TASK>
> > __dump_stack lib/dump_stack.c:88 [inline]
> > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> > kasan_report+0xbe/0x1f0 mm/kasan/report.c:495
> > check_region_inline mm/kasan/generic.c:183 [inline]
> > kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> > instrument_atomic_write include/linux/instrumented.h:86 [inline]
> > clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline]
> > kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742
> > process_one_work+0x996/0x1610 kernel/workqueue.c:2289
> > worker_thread+0x665/0x1080 kernel/workqueue.c:2436
> > kthread+0x2e9/0x3a0 kernel/kthread.c:376
> > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302
> > </TASK>
> >
> > Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
> > Reported-by: syzbot <syzkaller@googlegroups.com>
> > Signed-off-by: Eric Dumazet <edumazet@google.com>
> > Cc: Tom Herbert <tom@herbertland.com>
> > ---
> > net/kcm/kcmsock.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
> > index 1215c863e1c410fa9ba5b9c3706152decfb3ebac..27725464ec08fe2b5f2e86202636cbc895568098 100644
> > --- a/net/kcm/kcmsock.c
> > +++ b/net/kcm/kcmsock.c
> > @@ -1838,10 +1838,10 @@ static int kcm_release(struct socket *sock)
> > kcm = kcm_sk(sk);
> > mux = kcm->mux;
> >
> > + lock_sock(sk);
> > sock_orphan(sk);
> > kfree_skb(kcm->seq_skb);
> >
> > - lock_sock(sk);
> > /* Purge queue under lock to avoid race condition with tx_work trying
> > * to act when queue is nonempty. If tx_work runs after this point
> > * it will just return.
> > --
> > 2.38.0.rc1.362.ged0d419d3c-goog
> >
> > --
> > You received this message because you are subscribed to the Google Groups "syzkaller" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@googlegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller/20221012133412.519394-1-edumazet%40google.com.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] kcm: avoid potential race in kcm_tx_work
2022-10-12 13:34 [PATCH net] kcm: avoid potential race in kcm_tx_work Eric Dumazet
2022-10-12 14:00 ` Dmitry Vyukov
@ 2022-10-13 16:50 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2022-10-13 16:50 UTC (permalink / raw)
To: Eric Dumazet; +Cc: davem, kuba, pabeni, netdev, eric.dumazet, syzkaller, tom
Hello:
This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:
On Wed, 12 Oct 2022 13:34:12 +0000 you wrote:
> syzbot found that kcm_tx_work() could crash [1] in:
>
> /* Primarily for SOCK_SEQPACKET sockets */
> if (likely(sk->sk_socket) &&
> test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
> <<*>> clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
> sk->sk_write_space(sk);
> }
>
> [...]
Here is the summary with links:
- [net] kcm: avoid potential race in kcm_tx_work
https://git.kernel.org/netdev/net/c/ec7eede369fe
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-10-12 13:34 [PATCH net] kcm: avoid potential race in kcm_tx_work Eric Dumazet
2022-10-12 14:00 ` Dmitry Vyukov
2022-10-12 14:38 ` Eric Dumazet
2022-10-13 16:50 ` patchwork-bot+netdevbpf
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