2022-02-15 07:12:51

by Tom Rix

Subject: [PATCH v2] mctp: fix use after free

From: Tom Rix <[email protected]>

Clang static analysis reports this problem
route.c:425:4: warning: Use of memory after it is freed
trace_mctp_key_acquire(key);
^~~~~~~~~~~~~~~~~~~~~~~~~~~
When mctp_key_add() fails, key is freed but then is later
used in trace_mctp_key_acquire(). Add an else statement
to use the key only when mctp_key_add() is successful.

Fixes: 4f9e1ba6de45 ("mctp: Add tracepoints for tag/key handling")
Signed-off-by: Tom Rix <[email protected]>
---
v2: change the Fixes: line

net/mctp/route.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/mctp/route.c b/net/mctp/route.c
index 17e3482aa770..0c4c56e1bd6e 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -419,13 +419,14 @@ static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb)
* this function.
*/
rc = mctp_key_add(key, msk);
- if (rc)
+ if (rc) {
kfree(key);
+ } else {
+ trace_mctp_key_acquire(key);

- trace_mctp_key_acquire(key);
-
- /* we don't need to release key->lock on exit */
- mctp_key_unref(key);
+ /* we don't need to release key->lock on exit */
+ mctp_key_unref(key);
+ }
key = NULL;

} else {
--
2.26.3

2022-02-15 10:44:06

by Jeremy Kerr

Subject: Re: [PATCH v2] mctp: fix use after free

Hi Tom,

> Clang static analysis reports this problem
> route.c:425:4: warning: Use of memory after it is freed
>   trace_mctp_key_acquire(key);
>   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> When mctp_key_add() fails, key is freed but then is later
> used in trace_mctp_key_acquire().  Add an else statement
> to use the key only when mctp_key_add() is successful.
>
> Fixes: 4f9e1ba6de45 ("mctp: Add tracepoints for tag/key handling")
> Signed-off-by: Tom Rix <[email protected]>
> ---
> v2: change the Fixes: line

Super, thanks!

Acked-off-by: Jeremy Kerr <[email protected]>

Cheers,


Jeremy

2022-02-15 15:34:21

by patchwork-bot+netdevbpf

Subject: Re: [PATCH v2] mctp: fix use after free

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <[email protected]>:

On Mon, 14 Feb 2022 18:05:41 -0800 you wrote:
> From: Tom Rix <[email protected]>
>
> Clang static analysis reports this problem
> route.c:425:4: warning: Use of memory after it is freed
> trace_mctp_key_acquire(key);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> When mctp_key_add() fails, key is freed but then is later
> used in trace_mctp_key_acquire(). Add an else statement
> to use the key only when mctp_key_add() is successful.
>
> [...]

Here is the summary with links:
- [v2] mctp: fix use after free
https://git.kernel.org/netdev/net/c/7e5b6a5c8c44

You are awesome, thank you!
--
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