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

rtmutex: Use waiter::task instead of current in remove_waiter()

remove_waiter() is used by the slowlock paths, but it is also used for
proxy-lock rollback in rt_mutex_start_proxy_lock() when invoked from
futex_requeue().

In the latter case waiter::task is not current, but remove_waiter()
operates on current for the dequeue operation. That results in several
problems:

1. the rbtree dequeue happens without waiter::task::pi_lock being held

2. the waiter task's pi_blocked_on state is not cleared, which leaves a
   dangling pointer primed for UAF around.

3. rt_mutex_adjust_prio_chain() operates on the wrong top priority waiter
   task

Use waiter::task instead of current in all related operations in
remove_waiter() to cure those problems.

[ tglx: Fixup rt_mutex_adjust_prio_chain(), add a comment and amend the
changelog ]

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-43499
• https://git.kernel.org/stable/c/3bfdc63936dd4773109b7b8c280c0f3b5ae7d349
• https://git.kernel.org/stable/c/3fb7394a837740770f0d6b4b30567e60786a63f2
• https://git.kernel.org/stable/c/6d52dfcb2a5db86e346cf51f8fcf2071b8085166
• https://git.kernel.org/stable/c/88614876370aac8ad1050ad785a4c095ba17ac11
• https://git.kernel.org/stable/c/8a1fc8d698ac5e5916e3082a0f74450d71f9611f
• https://git.kernel.org/stable/c/d8cce4773c2b23d819baf5abedc62f7b430e8745
• http://www.openwall.com/lists/oss-security/2026/07/08/12
• https://git.kernel.org/stable/c/838ce5cb5d93c3ab8b27e75bc6ad905a94b752fd
• https://git.kernel.org/stable/c/f3fa3424bceb128d2be4b3745506b22844b87db7