CVE-2026-74601ring-buffer: Use current_context for safe per-CPU buffer swap

Official description

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Use current_context for safe per-CPU buffer swap The ring_buffer_swap_cpu() function currently checks the per-CPU committing counter to determine if a buffer is actively being written to before performing the swap. However, there exists a race window where this check can be bypassed: ring_buffer_lock_reserve cpu_buffer = buffer->buffers[cpu]; // cpu_buffer_a rb_reserve_next_event rb_start_commit // inc committing if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {...} __rb_reserve_next rb_move_tail rb_end_commit(cpu_buffer); // dec committing => 0 /* interrupt hits here, successfully swaps! */ local_inc(&cpu_buffer->committing); ring_buffer_unlock_commit cpu_buffer = buffer->buffers[cpu]; // cpu_buffer_b rb_commit rb_end_commit RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing)) // triggers warning The committing counter can temporarily drop to 0 during a single write operation (within rb_move_tail), creating a window where swap can succeed even though the write is still in progress. This leads to inconsistent buffer state and triggers the RB_WARN_ON in rb_commit(). Replace the committing counter check with current_context checks, which are set at the entry of ring_buffer_lock_reserve() and remain valid throughout the entire write operation, providing a reliable indicator of buffer busy state during swap.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/26662bc8fced1d668fa1aa146eda085bfc67bd0b
• https://git.kernel.org/stable/c/6b524e6b234e45c7f5f90d13b042c6f57f80105c
• https://git.kernel.org/stable/c/597f279b7b4a06412e3d965e98cc36e181cdbede
• https://git.kernel.org/stable/c/22709117d9ae95e52673685f98caac7c356a8227
• https://git.kernel.org/stable/c/ad7e10c7ea89af45ac1bf1814855d45da472703d
• https://git.kernel.org/stable/c/5b926fb04cb9ef3156dcf88c69a59d3d1a1c4f9f
• https://git.kernel.org/stable/c/5e6e2a18c20e88167d414f666032792e8bf19b80
• https://git.kernel.org/stable/c/f27bdc43077e4fcb5557dfc315ee8d91e741f483