Re: [PATCH] perf: fix WARNING in perf_event_open

[Jiri Olsa]

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@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>

hi,
Mark suggested another fix earlier [1], but I haven't seen the formal patch yet

jirka


[1] https://lore.kernel.org/linux-perf-users/ZXwubNIxKH9s7DWt@FVFF77S0Q05N/

> ---
>  kernel/events/core.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> 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
>