Re: [PATCH v4 02/10] perf tools: Try linked debug files for DSO debug info

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] perf dso: DEBUGLINK path resolution flaws in dso__read_binary_type_filename
--

commit 0c61bd07a4d26ed6f7bfc347b3ec0fe6ffc13ca0
Author: Namhyung Kim <namhyung@kernel.org>

perf tools: Try linked debug files for DSO debug info

This commit modifies dso__find_dbginfo_type() to include
DSO_BINARY_TYPE__DEBUGLINK in its search array. This allows perf to follow
.gnu_debuglink to locate debug information in separate files.

> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index df03f84c97235..913877b84b2d4 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -2111,6 +2111,7 @@ void dso__find_dbginfo_type(struct dso *dso)
>  		DSO_BINARY_TYPE__OPENEMBEDDED_DEBUGINFO,
>  		DSO_BINARY_TYPE__BUILDID_DEBUGINFO,
>  		DSO_BINARY_TYPE__SYSTEM_PATH_DSO,
> +		DSO_BINARY_TYPE__DEBUGLINK,

[Severity: Medium]
Enabling DSO_BINARY_TYPE__DEBUGLINK here exposes path resolution regressions in
dso__read_binary_type_filename().

If the filename lacks slashes, does this logic create an empty string for
dso_dir, breaking relative paths?

tools/perf/util/dso.c:dso__read_binary_type_filename() {
	...
	last_slash = filename + len;
	while (last_slash != filename && *last_slash != '/')
		last_slash--;

	strncpy(dso_dir, filename, last_slash - filename);
	dso_dir[last_slash-filename] = '\0';
	...
}

Additionally, does this direct host filesystem I/O bypass the container mount
namespace (/proc/<pid>/root/) fallback context?

tools/perf/util/dso.c:dso__read_binary_type_filename() {
	...
	if (!is_regular_file(filename)) {
		ret = -1;
		break;
	}

	ret = filename__read_debuglink(filename, symfile, PATH_MAX);
	...
}

Finally, does this inject the symfs-prefixed dso_dir into the middle of the
/usr/lib/debug path, searching the host filesystem instead of the symfs
chroot?

tools/perf/util/dso.c:dso__read_binary_type_filename() {
	...
	for (i = 0; i < ARRAY_SIZE(debuglink_paths); i++) {
		snprintf(filename, size,
				debuglink_paths[i], dso_dir, symfile);
	...
}

>  		DSO_BINARY_TYPE__NOT_FOUND,
>  	};
>  	const enum dso_binary_type *type;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261012234654.60666-1-namhyung@kernel.org?part=2