* [PATCH net] kcm: Fix memory leak in error path of kcm_sendmsg()
@ 2023-09-02 16:52 Shigeru Yoshida
2023-09-05 8:09 ` Paolo Abeni
0 siblings, 1 reply; 3+ messages in thread
From: Shigeru Yoshida @ 2023-09-02 16:52 UTC (permalink / raw)
To: davem, edumazet, kuba, pabeni
Cc: netdev, linux-kernel, Shigeru Yoshida, syzbot+6f98de741f7dbbfc4ccb
syzbot reported a memory leak like below [1]:
BUG: memory leak
unreferenced object 0xffff88810b088c00 (size 240):
comm "syz-executor186", pid 5012, jiffies 4294943306 (age 13.680s)
hex dump (first 32 bytes):
00 89 08 0b 81 88 ff ff 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff83e5d5ff>] __alloc_skb+0x1ef/0x230 net/core/skbuff.c:634
[<ffffffff84606e59>] alloc_skb include/linux/skbuff.h:1289 [inline]
[<ffffffff84606e59>] kcm_sendmsg+0x269/0x1050 net/kcm/kcmsock.c:815
[<ffffffff83e479c6>] sock_sendmsg_nosec net/socket.c:725 [inline]
[<ffffffff83e479c6>] sock_sendmsg+0x56/0xb0 net/socket.c:748
[<ffffffff83e47f55>] ____sys_sendmsg+0x365/0x470 net/socket.c:2494
[<ffffffff83e4c389>] ___sys_sendmsg+0xc9/0x130 net/socket.c:2548
[<ffffffff83e4c536>] __sys_sendmsg+0xa6/0x120 net/socket.c:2577
[<ffffffff84ad7bb8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<ffffffff84ad7bb8>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
In kcm_sendmsg(), newly allocated socket buffers can be added to skb->next. If
an error occurred and jumped to out_error label, those newly allocated socket
buffers can be leaked. This patch fixes this issue by remembering the last
allocated socket buffer in kcm_tx_msg(head)->last_skb.
Link: https://syzkaller.appspot.com/bug?extid=6f98de741f7dbbfc4ccb [1]
Reported-by: syzbot+6f98de741f7dbbfc4ccb@syzkaller.appspotmail.com
Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
---
net/kcm/kcmsock.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 393f01b2a7e6..34d4062f639a 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -939,6 +939,8 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
if (head != kcm->seq_skb)
kfree_skb(head);
+ else if (copied)
+ kcm_tx_msg(head)->last_skb = skb;
err = sk_stream_error(sk, msg->msg_flags, err);
--
2.41.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net] kcm: Fix memory leak in error path of kcm_sendmsg()
2023-09-02 16:52 [PATCH net] kcm: Fix memory leak in error path of kcm_sendmsg() Shigeru Yoshida
@ 2023-09-05 8:09 ` Paolo Abeni
2023-09-07 15:14 ` Shigeru Yoshida
0 siblings, 1 reply; 3+ messages in thread
From: Paolo Abeni @ 2023-09-05 8:09 UTC (permalink / raw)
To: Shigeru Yoshida, davem, edumazet, kuba
Cc: netdev, linux-kernel, syzbot+6f98de741f7dbbfc4ccb
Hello,
On Sun, 2023-09-03 at 01:52 +0900, Shigeru Yoshida wrote:
> syzbot reported a memory leak like below [1]:
>
> BUG: memory leak
> unreferenced object 0xffff88810b088c00 (size 240):
> comm "syz-executor186", pid 5012, jiffies 4294943306 (age 13.680s)
> hex dump (first 32 bytes):
> 00 89 08 0b 81 88 ff ff 00 00 00 00 00 00 00 00 ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<ffffffff83e5d5ff>] __alloc_skb+0x1ef/0x230 net/core/skbuff.c:634
> [<ffffffff84606e59>] alloc_skb include/linux/skbuff.h:1289 [inline]
> [<ffffffff84606e59>] kcm_sendmsg+0x269/0x1050 net/kcm/kcmsock.c:815
> [<ffffffff83e479c6>] sock_sendmsg_nosec net/socket.c:725 [inline]
> [<ffffffff83e479c6>] sock_sendmsg+0x56/0xb0 net/socket.c:748
> [<ffffffff83e47f55>] ____sys_sendmsg+0x365/0x470 net/socket.c:2494
> [<ffffffff83e4c389>] ___sys_sendmsg+0xc9/0x130 net/socket.c:2548
> [<ffffffff83e4c536>] __sys_sendmsg+0xa6/0x120 net/socket.c:2577
> [<ffffffff84ad7bb8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> [<ffffffff84ad7bb8>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
> [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> In kcm_sendmsg(), newly allocated socket buffers can be added to skb->next. If
> an error occurred and jumped to out_error label, those newly allocated socket
> buffers can be leaked. This patch fixes this issue by remembering the last
> allocated socket buffer in kcm_tx_msg(head)->last_skb.
I think the root cause should be clarified a little more. When the
'head' skb will be freed, all the frag_list skbs will be released, too.
AFAICS the issue is that in case of error after copying some bytes,
kcm_tx_msg(head)->last_skb is left unmodified and such reference is
used as the cursor to append newly allocated skbs to 'head'.
A later kcm_sendmsg will use an obsoleted 'last_skb' reference,
corrupting the 'head' frag_list and causing the leak.
The fix looks correct, but could you please send a v2 with an
updated/more extensive commit message?
> Link: https://syzkaller.appspot.com/bug?extid=6f98de741f7dbbfc4ccb [1]
> Reported-by: syzbot+6f98de741f7dbbfc4ccb@syzkaller.appspotmail.com
> Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
> Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Additionally please feed the patch to syzbot, so it can verify the fix,
and add the relevant tag.
Thanks,
Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net] kcm: Fix memory leak in error path of kcm_sendmsg()
2023-09-05 8:09 ` Paolo Abeni
@ 2023-09-07 15:14 ` Shigeru Yoshida
0 siblings, 0 replies; 3+ messages in thread
From: Shigeru Yoshida @ 2023-09-07 15:14 UTC (permalink / raw)
To: Paolo Abeni
Cc: netdev, linux-kernel, syzbot+6f98de741f7dbbfc4ccb, davem, edumazet, kuba
Hi Paolo,
On 9/5/23 17:09, Paolo Abeni wrote:
> Hello,
>
> On Sun, 2023-09-03 at 01:52 +0900, Shigeru Yoshida wrote:
>> syzbot reported a memory leak like below [1]:
>>
>> BUG: memory leak
>> unreferenced object 0xffff88810b088c00 (size 240):
>> comm "syz-executor186", pid 5012, jiffies 4294943306 (age 13.680s)
>> hex dump (first 32 bytes):
>> 00 89 08 0b 81 88 ff ff 00 00 00 00 00 00 00 00 ................
>> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>> backtrace:
>> [<ffffffff83e5d5ff>] __alloc_skb+0x1ef/0x230 net/core/skbuff.c:634
>> [<ffffffff84606e59>] alloc_skb include/linux/skbuff.h:1289 [inline]
>> [<ffffffff84606e59>] kcm_sendmsg+0x269/0x1050 net/kcm/kcmsock.c:815
>> [<ffffffff83e479c6>] sock_sendmsg_nosec net/socket.c:725 [inline]
>> [<ffffffff83e479c6>] sock_sendmsg+0x56/0xb0 net/socket.c:748
>> [<ffffffff83e47f55>] ____sys_sendmsg+0x365/0x470 net/socket.c:2494
>> [<ffffffff83e4c389>] ___sys_sendmsg+0xc9/0x130 net/socket.c:2548
>> [<ffffffff83e4c536>] __sys_sendmsg+0xa6/0x120 net/socket.c:2577
>> [<ffffffff84ad7bb8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>> [<ffffffff84ad7bb8>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
>> [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>
>> In kcm_sendmsg(), newly allocated socket buffers can be added to skb->next. If
>> an error occurred and jumped to out_error label, those newly allocated socket
>> buffers can be leaked. This patch fixes this issue by remembering the last
>> allocated socket buffer in kcm_tx_msg(head)->last_skb.
>
> I think the root cause should be clarified a little more. When the
> 'head' skb will be freed, all the frag_list skbs will be released, too.
>
> AFAICS the issue is that in case of error after copying some bytes,
> kcm_tx_msg(head)->last_skb is left unmodified and such reference is
> used as the cursor to append newly allocated skbs to 'head'.
>
> A later kcm_sendmsg will use an obsoleted 'last_skb' reference,
> corrupting the 'head' frag_list and causing the leak.
>
> The fix looks correct, but could you please send a v2 with an
> updated/more extensive commit message?
Thank you so much for your feedback. Yes, I'll send a v2 patch
with the detailed root cause.
>
>> Link: https://syzkaller.appspot.com/bug?extid=6f98de741f7dbbfc4ccb [1]
>> Reported-by: syzbot+6f98de741f7dbbfc4ccb@syzkaller.appspotmail.com
>> Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
>> Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
>
> Additionally please feed the patch to syzbot, so it can verify the fix,
> and add the relevant tag.
I got it. I'll try syzbot for the v2 patch.
Thanks,
Shigeru
>
> Thanks,
>
> Paolo
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-09-07 15:28 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2023-09-02 16:52 [PATCH net] kcm: Fix memory leak in error path of kcm_sendmsg() Shigeru Yoshida
2023-09-05 8:09 ` Paolo Abeni
2023-09-07 15:14 ` Shigeru Yoshida
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