Re: [PATCH v6 2/2] perf evsel: Find process with busy PMUs for EBUSY

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The file descriptor `fdinfo_fd` is permanently leaked on all successful open paths.
--

commit 89c8fa0a46a0a7739ea59073f27c6161911eb75b
Author: Chun-Tse Shao <ctshao@google.com>

perf evsel: Find process with busy PMUs for EBUSY

This commit parses the fdinfo of perf events to extract the PMU type.
It then compares this type with the failed event to accurately report
the specific processes that are causing an EBUSY error.

> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 2ee87fd84d3ea..f6282099320ee 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
[ ... ]
> @@ -3969,29 +3970,61 @@ static int dump_perf_event_processes(char *msg, size_t size)
>  				continue;
>  			/* Take care as readlink doesn't null terminate the string. */
>  			if (!strncmp(buf, "anon_inode:[perf_event]", link_size)) {
> -				int cmdline_fd;
> -				ssize_t cmdline_size;
> -
> -				scnprintf(buf, sizeof(buf), "%s/cmdline", proc_entry->d_name);
> -				cmdline_fd = openat(dirfd(proc_dir), buf, O_RDONLY);
> -				if (cmdline_fd == -1)
> -					continue;
> -				cmdline_size = read(cmdline_fd, buf, sizeof(buf) - 1);
> -				close(cmdline_fd);
> -				if (cmdline_size < 0)
> +				int fdinfo_fd;
> +				ssize_t fdinfo_size;
> +				char *line;
> +				u32 perf_event_type = UINT32_MAX;
> +
> +				/* Let's check the PMU type reserved by this process */
> +				scnprintf(buf, sizeof(buf), "%s/fdinfo/%s",
> +					  proc_entry->d_name, fd_entry->d_name);
> +				fdinfo_fd = openat(dirfd(proc_dir), buf, O_RDONLY);
> +				fdinfo_size = read(fdinfo_fd, buf, sizeof(buf) - 1);
> +				if (fdinfo_size < 0)
>  					continue;

Is fdinfo_fd leaked here and on subsequent execution paths in this loop?

Since this loop scans potentially thousands of file descriptors across all
active processes in /proc, could leaking a file descriptor for every
discovered perf event rapidly exhaust the process's file descriptor limit
and lead to EMFILE?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260518174159.1177549-1-ctshao@google.com?part=2