CVE-2026-53085bpf: fix mm lifecycle in open-coded task_vma iterator

Official description

In the Linux kernel, the following vulnerability has been resolved: bpf: fix mm lifecycle in open-coded task_vma iterator The open-coded task_vma iterator reads task->mm locklessly and acquires mmap_read_trylock() but never calls mmget(). If the task exits concurrently, the mm_struct can be freed as it is not SLAB_TYPESAFE_BY_RCU, resulting in a use-after-free. Safely read task->mm with a trylock on alloc_lock and acquire an mm reference. Drop the reference via bpf_iter_mmput_async() in _destroy() and error paths. bpf_iter_mmput_async() is a local wrapper around mmput_async() with a fallback to mmput() on !CONFIG_MMU. Reject irqs-disabled contexts (including NMI) up front. Operations used by _next() and _destroy() (mmap_read_unlock, bpf_iter_mmput_async) take spinlocks with IRQs disabled (pool->lock, pi_lock). Running from NMI or from a tracepoint that fires with those locks held could deadlock. A trylock on alloc_lock is used instead of the blocking task_lock() (get_task_mm) to avoid a deadlock when a softirq BPF program iterates a task that already holds its alloc_lock on the same CPU.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/239cec25a22662dbd80f57d94b38178c8be95269
• https://git.kernel.org/stable/c/d0862de7c866c5bd7c32531f66738c21197af888
• https://git.kernel.org/stable/c/43683bb280330f3d36f0f2a3932a4867b9603e9c
• https://git.kernel.org/stable/c/d8e27d2d22b6e2df3a0125b8c08e9aace38c954c
• https://access.redhat.com/security/cve/CVE-2026-53085 vdb-entry, x_refsource_REDHAT
• RHBZ#2492404 issue-tracking, x_refsource_REDHAT
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53085.json x_sadp-csaf-vex