A use-after-free vulnerability in the Linux kernel's net/sched: cls_fw component can be exploited to achieve local privilege escalation. When fw_change() is called on an existing filter, the whole tcf_result struct is always copied into the new instance of the filter. This causes a problem when updating a filter bound to a class, as tcf_unbind_filter() is always called on the old instance in the success path, decreasing filter_cnt of the still referenced class and allowing it to be deleted, leading to a use-after-free. We recommend upgrading past commit 76e42ae831991c828cffa8c37736ebfb831ad5ec.
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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
| Link | Tags |
|---|---|
| https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=76e42ae831991c828cffa8c37736ebfb831ad5ec | patch mailing list vendor advisory issue tracking |
| https://kernel.dance/76e42ae831991c828cffa8c37736ebfb831ad5ec | patch vendor advisory |
| https://www.debian.org/security/2023/dsa-5492 | third party advisory |
| https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html | mailing list third party advisory vdb entry |