Re: [PATCH] perf: fix WARNING in perf_event_open

Mark Rutland
2024-01-05T11:32:32Z

On Tue, Dec 26, 2023 at 03:25:15PM +0800, Edward Adam Davis wrote:
> The new version of __perf_event_read_size() only has a read action and does not
> require a mutex, so the mutex assertion in the original loop is removed.
>
> Fixes: 382c27f4ed28 ("perf: Fix perf_event_validate_size()")
> Reported-and-tested-by: syzbot+07144c543a5c002c7305@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
> kernel/events/core.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)

Thanks for the patch; this should be fixed by:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.7-rc6&id=7e2c1e4b34f07d9aa8937fab88359d4a0fce468e

... which is in v6.7-rc6.

Mark.

>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 9efd0d7775e7..e71e61b46416 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1924,6 +1924,10 @@ static void perf_event__id_header_size(struct perf_event *event)
> event->id_header_size = size;
> }
>
> +#define read_for_each_sibling_event(sibling, event) \
> + if ((event)->group_leader == (event)) \
> + list_for_each_entry((sibling), &(event)->sibling_list, sibling_list)
> +
> /*
> * Check that adding an event to the group does not result in anybody
> * overflowing the 64k event limit imposed by the output buffer.
> @@ -1957,7 +1961,7 @@ static bool perf_event_validate_size(struct perf_event *event)
> if (event == group_leader)
> return true;
>
> - for_each_sibling_event(sibling, group_leader) {
> + read_for_each_sibling_event(sibling, group_leader) {
> if (__perf_event_read_size(sibling->attr.read_format,
> group_leader->nr_siblings + 1) > 16*1024)
> return false;
> --
> 2.43.0
>