[oss-security] CVE request Linux kernel: forbid uaddr == uaddr2 in futex_wait_requeue_pi() to avoid null dereference

Hello,

Linux kernel built with the fast userspace mutexes(CONFIG_FUTEX) support is vulnerable to a NULL pointer dereference flaw. It could occur when a waiting task requests wait to be re-queued from non-PI futex to a PI-aware futex via FUTEX_WAIT_REQUEUE_PI operation.

An unprivileged user/program could use this flaw to crash the system kernel resulting in DoS.

Upstream fix:

-> https://git.kernel.org/linus/6f7b0a2a5c0fb03be7c25bd1745baa50582348ef

Introduced in:

-> https://git.kernel.org/linus/52400ba946759af28442dee6265c5c0180ac7122

Thank you.

Prasad J Pandit / Red Hat Security Response Team