High · published June 18, 2025
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix KASAN use-after-free Read in compute_effective_progs
Syzbot found a Use After Free bug in compute_effective_progs().
The reproducer creates a number of BPF links, and causes a fault
injected alloc to fail, while calling bpf_link_detach on them.
Link detach triggers the link to be freed by bpf_link_free(),
which calls __cgroup_bpf_detach() and update_effective_progs().
If the memory allocation in this function fails, the function restores
the pointer to the bpf_cgroup_link on the cgroup list, but the memory
gets freed just after it returns. After this, every subsequent call to
update_effective_progs() causes this already deallocated pointer to be
dereferenced in prog_list_length(), and triggers KASAN UAF error.
To fix this issue don't preserve the pointer to the prog or link in the
list, but remove it and replace it with a dummy prog without shrinking
the table. The subsequent call to __cgroup_bpf_detach() or
__cgroup_bpf_detach() will correct it.
| Product | Versions | Fixed in |
|---|---|---|
| linux/linux_kernel | ≥ 5.7, < 5.10.138 | 5.10.138 |
| linux/linux_kernel | ≥ 5.11, < 5.15.61 | 5.15.61 |
| linux/linux_kernel | ≥ 5.16, < 5.18.18 | 5.18.18 |
| linux/linux_kernel | ≥ 5.19, < 5.19.2 | 5.19.2 |