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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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bpf: Sync pending IRQ work before freeing ring buffer

Fix a race where irq_work can be queued in bpf_ringbuf_commit()
but the ring buffer is freed before the work executes.
In the syzbot reproducer, a BPF program attached to sched_switch
triggers bpf_ringbuf_commit(), queuing an irq_work. If the ring buffer
is freed before this work executes, the irq_work thread may accesses
freed memory.
Calling `irq_work_sync(&rb->work)` ensures that all pending irq_work
complete before freeing the buffer.

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: syzbot+2617fc732430968b45d2@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2617fc732430968b45d2
Tested-by: syzbot+2617fc732430968b45d2@syzkaller.appspotmail.com
Signed-off-by: Noorain Eqbal <nooraineqbal@gmail.com>
Link: https://lore.kernel.org/r/20251020180301.103366-1-nooraineqbal@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

authored by

Noorain Eqbal and committed by
Alexei Starovoitov 4e907763 6548d364

+2
+2
kernel/bpf/ringbuf.c
··· 216 216 217 217 static void bpf_ringbuf_free(struct bpf_ringbuf *rb) 218 218 { 219 + irq_work_sync(&rb->work); 220 + 219 221 /* copy pages pointer and nr_pages to local variable, as we are going 220 222 * to unmap rb itself with vunmap() below 221 223 */