[PATCH v4] net/rose: Fix Use-After-Free in rose_ioctl

[PATCH v4] net/rose: Fix Use-After-Free in rose_ioctl

[Hyunwoo Kim]

Because rose_ioctl() accesses sk->sk_receive_queue
without holding a sk->sk_receive_queue.lock, it can
cause a race with rose_accept().
A use-after-free for skb occurs with the following flow.
```
rose_ioctl() -> skb_peek()
rose_accept() -> skb_dequeue() -> kfree_skb()
```
Add sk->sk_receive_queue.lock to rose_ioctl() to fix this issue.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
---
v1 -> v2: Use sk->sk_receive_queue.lock instead of lock_sock.
v2 -> v3: Change spin_lock to spin_lock_irq
v3 -> v4: Delete old comments
---
 net/rose/af_rose.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c
index 0cc5a4e19900..ecb91ad4ce63 100644
--- a/net/rose/af_rose.c
+++ b/net/rose/af_rose.c
@@ -1315,9 +1315,11 @@ static int rose_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 	case TIOCINQ: {
 		struct sk_buff *skb;
 		long amount = 0L;
-		/* These two are safe on a single CPU system as only user tasks fiddle here */
+
+		spin_lock_irq(&sk->sk_receive_queue.lock);
 		if ((skb = skb_peek(&sk->sk_receive_queue)) != NULL)
 			amount = skb->len;
+		spin_unlock_irq(&sk->sk_receive_queue.lock);
 		return put_user(amount, (unsigned int __user *) argp);
 	}
 
-- 
2.25.1

Re: [PATCH v4] net/rose: Fix Use-After-Free in rose_ioctl

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Sat, 9 Dec 2023 05:05:38 -0500 you wrote:
> Because rose_ioctl() accesses sk->sk_receive_queue
> without holding a sk->sk_receive_queue.lock, it can
> cause a race with rose_accept().
> A use-after-free for skb occurs with the following flow.
> ```
> rose_ioctl() -> skb_peek()
> rose_accept() -> skb_dequeue() -> kfree_skb()
> ```
> Add sk->sk_receive_queue.lock to rose_ioctl() to fix this issue.
> 
> [...]

Here is the summary with links:
  - [v4] net/rose: Fix Use-After-Free in rose_ioctl
    https://git.kernel.org/netdev/net/c/810c38a369a0

You are awesome, thank you!
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