Re: [PATCH v2] tracing/uprobe: Add missing PID filter for uretprobe

[Oleg Nesterov <oleg@xxxxxxxxxx>]

On 08/30, Oleg Nesterov wrote:
>
> 	- This patch won't fix all problems because uprobe_perf_filter()
> 	  filters by mm, not by pid. The changelog/patch assumes that it
> 	  is a "PID filter", but it is not.
>
>	  See https://lore.kernel.org/linux-trace-kernel/20240825224018.GD3906@xxxxxxxxxx/

Let me provide another example.

spawn.c:

	#include <spawn.h>
	#include <unistd.h>

	int main(int argc, char *argv[])
	{
		int pid;
		sleep(3); // wait for bpftrace to start
		posix_spawn(&pid, argv[1], NULL, NULL, argv+1, NULL);
		for (;;)
			pause();
	}

Now,

	$ ./spawn /usr/bin/true &
	bpftrace -p $! -e 'uprobe:/usr/lib64/libc.so.6:sigprocmask { printf("%d\n", pid); }'
	[2] 212851
	Attaching 1 probe...
	212855
	^C
	$ ./spawn /xxxxxxxxxxxx &
	bpftrace -p $! -e 'uprobe:/usr/lib64/libc.so.6:_exit { printf("%d\n", pid); }'
	[3] 212860
	Attaching 1 probe...
	212865
	^C

This patch can't help in this case.

Oleg.