Description

In the Linux kernel, the following vulnerability has been resolved: apparmor: avoid per-cpu hold underflow in aa_get_buffer When aa_get_buffer() pulls from the per-cpu list it unconditionally decrements cache->hold. If hold reaches 0 while count is still non-zero, the unsigned decrement wraps to UINT_MAX. This keeps hold non-zero for a very long time, so aa_put_buffer() never returns buffers to the global list, which can starve other CPUs and force repeated kmalloc(aa_g_path_max) allocations. Guard the decrement so hold never underflows.

References 4

• git.kernel.org https://git.kernel.org/stable/c/202824a1f89a9786c20a3d646a7c88d223abb1b2
• git.kernel.org https://git.kernel.org/stable/c/4bcddd0f6b2e52b4c7b520e4d36a115caf5b7169
• git.kernel.org https://git.kernel.org/stable/c/640cf2f09575c9dc344b3f7be2498d31e3923ead
• git.kernel.org https://git.kernel.org/stable/c/80c334acc6d0bee8605a358a33e69b4aea1ffb92

Remediation