[PATCH] tipc: Fix potential tipc_aead refcnt leak in tipc_crypto_rcv

[PATCH] tipc: Fix potential tipc_aead refcnt leak in tipc_crypto_rcv

[Xiyu Yang]

tipc_crypto_rcv() invokes tipc_aead_get(), which returns a reference of
the tipc_aead object to "aead" with increased refcnt.

When tipc_crypto_rcv() returns, the original local reference of "aead"
becomes invalid, so the refcount should be decreased to keep refcount
balanced.

The issue happens in one error path of tipc_crypto_rcv(). When TIPC
message decryption status is EINPROGRESS or EBUSY, the function forgets
to decrease the refcnt increased by tipc_aead_get() and causes a refcnt
leak.

Fix this issue by calling tipc_aead_put() on the error path when TIPC
message decryption status is EINPROGRESS or EBUSY.

Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
---
 net/tipc/crypto.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index c8c47fc72653..8c47ded2edb6 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -1712,6 +1712,7 @@ int tipc_crypto_rcv(struct net *net, struct tipc_crypto *rx,
 	case -EBUSY:
 		this_cpu_inc(stats->stat[STAT_ASYNC]);
 		*skb = NULL;
+		tipc_aead_put(aead);
 		return rc;
 	default:
 		this_cpu_inc(stats->stat[STAT_NOK]);
-- 
2.7.4

Re: [PATCH] tipc: Fix potential tipc_aead refcnt leak in tipc_crypto_rcv

[David Miller]

From: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Date: Wed, 15 Apr 2020 16:39:56 +0800

> tipc_crypto_rcv() invokes tipc_aead_get(), which returns a reference of
> the tipc_aead object to "aead" with increased refcnt.
> 
> When tipc_crypto_rcv() returns, the original local reference of "aead"
> becomes invalid, so the refcount should be decreased to keep refcount
> balanced.
> 
> The issue happens in one error path of tipc_crypto_rcv(). When TIPC
> message decryption status is EINPROGRESS or EBUSY, the function forgets
> to decrease the refcnt increased by tipc_aead_get() and causes a refcnt
> leak.
> 
> Fix this issue by calling tipc_aead_put() on the error path when TIPC
> message decryption status is EINPROGRESS or EBUSY.
> 
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>

Applied and queued up for -stable.

This code is harder to audit than it needs to be due to the special
casing of things like -ENOKEY etc.  It should rather explicitly handle
the NULL test on aead in this top-level piece of code, which would
make the validation of aead reference counting much more explicit and
clear.