On 6/26/21 8:11 PM, Rustam Kovhaev wrote:
kmemleak scans struct page, but it does not scan the page content. if we allocate some memory with kmalloc(), then allocate page with alloc_page(), and if we put kmalloc pointer somewhere inside that page, kmemleak will report kmalloc pointer as a false positive. we can instruct kmemleak to scan the memory area by calling kmemleak_alloc()/kmemleak_free(), but part of struct bpf_ringbuf is mmaped to user space, and if struct bpf_ringbuf changes we would have to revisit and review size argument in kmemleak_alloc(), because we do not want kmemleak to scan the user space memory. let's simplify things and use kmemleak_not_leak() here. Link: https://lore.kernel.org/lkml/YNTAqiE7CWJhOK2M@nuc10/ Link: https://lore.kernel.org/lkml/20210615101515.GC26027@xxxxxxx/ Link: https://syzkaller.appspot.com/bug?extid=5d895828587f49e7fe9b Reported-and-tested-by: syzbot+5d895828587f49e7fe9b@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Rustam Kovhaev <rkovhaev@xxxxxxxxx>
Applied, thanks! (Also included Andrii's prior analysis as well to the commit log so there's a bit more context if we need to revisit in future [0].) [0] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=ccff81e1d028bbbf8573d3364a87542386c707bf
