CVE-2024-50186

In the Linux kernel, the following vulnerability has been resolved:

net: explicitly clear the sk pointer, when pf->create fails

We have recently noticed the exact same KASAN splat as in commit 6cd4a78d962b (net: do not leave a dangling sk pointer, when socket creation fails). The problem is that commit did not fully address the problem, as some pf->create implementations do not use sk_common_release in their error paths.

For example, we can use the same reproducer as in the above commit, but changing ping to arping. arping uses AF_PACKET socket and if packet_create fails, it will just sk_free the allocated sk object.

While we could chase all the pf->create implementations and make sure they NULL the freed sk object on error from the socket, we cant guarantee future protocols will not make the same mistake.

So it is easier to just explicitly NULL the sk pointer upon return from pf->create in __sock_create. We do know that pf->create always releases the allocated sk object on error, so if the pointer is not NULL, it is definitely dangling.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/563e6892e21d6ecabdf62103fc4e7b326d212334
• https://git.kernel.org/stable/c/631083143315d1b192bd7d915b967b37819e88ea
• https://git.kernel.org/stable/c/8e1b72fd74bf9da3b099d09857f4e7f114f38e12
• https://git.kernel.org/stable/c/b7d22a79ff4e962b8af5ffe623abd1d6c179eb9f
• https://git.kernel.org/stable/c/daf462ff3cde6ecf22b98d9ae770232c10d28de2
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html