Description

In the Linux kernel, the following vulnerability has been resolved: bpf, cpumap: Make sure kthread is running before map update returns The following warning was reported when running stress-mode enabled xdp_redirect_cpu with some RT threads: ------------[ cut here ]------------ WARNING: CPU: 4 PID: 65 at kernel/bpf/cpumap.c:135 CPU: 4 PID: 65 Comm: kworker/4:1 Not tainted 6.5.0-rc2+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) Workqueue: events cpu_map_kthread_stop RIP: 0010:put_cpu_map_entry+0xda/0x220 ...... Call Trace: <TASK> ? show_regs+0x65/0x70 ? __warn+0xa5/0x240 ...... ? put_cpu_map_entry+0xda/0x220 cpu_map_kthread_stop+0x41/0x60 process_one_work+0x6b0/0xb80 worker_thread+0x96/0x720 kthread+0x1a5/0x1f0 ret_from_fork+0x3a/0x70 ret_from_fork_asm+0x1b/0x30 </TASK> The root cause is the same as commit 436901649731 ("bpf: cpumap: Fix memory leak in cpu_map_update_elem"). The kthread is stopped prematurely by kthread_stop() in cpu_map_kthread_stop(), and kthread() doesn't call cpu_map_kthread_run() at all but XDP program has already queued some frames or skbs into ptr_ring. So when __cpu_map_ring_cleanup() checks the ptr_ring, it will find it was not emptied and report a warning. An alternative fix is to use __cpu_map_ring_cleanup() to drop these pending frames or skbs when kthread_stop() returns -EINTR, but it may confuse the user, because these frames or skbs have been handled correctly by XDP program. So instead of dropping these frames or skbs, just make sure the per-cpu kthread is running before __cpu_map_entry_alloc() returns. After apply the fix, the error handle for kthread_stop() will be unnecessary because it will always return 0, so just remove it.

Weaknesses 1

Affected Products 7

References 4

• git.kernel.org https://git.kernel.org/stable/c/640a604585aa30f93e39b17d4d6ba69fcb1e66c9
  Patch
• git.kernel.org https://git.kernel.org/stable/c/7a1178a3671b40746830d355836b72e47ceb2490
  Patch
• git.kernel.org https://git.kernel.org/stable/c/b44d28b98f185d2f2348aa3c3636838c316f889e
  Patch
• git.kernel.org https://git.kernel.org/stable/c/ecb45b852af5e88257020b88bea5ff0798d72aca
  Patch

Remediation

• git.kernel.org https://git.kernel.org/stable/c/640a604585aa30f93e39b17d4d6ba69fcb1e66c9
  Patch
• git.kernel.org https://git.kernel.org/stable/c/7a1178a3671b40746830d355836b72e47ceb2490
  Patch
• git.kernel.org https://git.kernel.org/stable/c/b44d28b98f185d2f2348aa3c3636838c316f889e
  Patch
• git.kernel.org https://git.kernel.org/stable/c/ecb45b852af5e88257020b88bea5ff0798d72aca
  Patch