Re: [PATCH v5 2/4] perf synthetic-events: Fix line synchronization, bounds, and truncation bugs in proc maps reader

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Stale build ID leakage across kernel module synthesis due to removed loop cleanup.
--

--- Patch [2]: [PATCH v5 2/4] perf synthetic-events: Fix line synchronization, bounds, and truncation bugs in proc maps reader ---
commit 7ed1842aa319aa810201b4aedeba9993fa02dfd6
Author: Ian Rogers <irogers@google.com>

perf synthetic-events: Fix line synchronization, bounds, and truncation bugs in proc maps reader

This commit addresses logic and boundary bugs in read_proc_maps_line() and its
caller. It ensures parsing failures invoke safe drain paths, clamps pathname
extraction sizes, and correctly handles timeout flags.

> diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
> index 5307d707711d8..e379174ae002d 100644
> --- a/tools/perf/util/synthetic-events.c
> +++ b/tools/perf/util/synthetic-events.c
[ ... ]
> @@ -703,11 +783,6 @@ static int perf_event__synthesize_modules_maps_cb(struct map *map, void *data)
>  
>  		memcpy(event->mmap2.filename, dso__long_name(dso), dso__long_name_len(dso) + 1);
>  
> -		/* Clear stale build ID from previous module iteration */
> -		event->mmap2.header.misc &= ~PERF_RECORD_MISC_MMAP_BUILD_ID;
> -		memset(event->mmap2.build_id, 0, sizeof(event->mmap2.build_id));
> -		event->mmap2.build_id_size = 0;
> -

[Severity: Medium]
Does this removal cause stale build IDs to leak across module syntheses?

Since the event structure is allocated once and reused across all kernel modules
in the loop, if perf_record_mmap2__read_build_id() fails to read a build ID for
a subsequent module, it seems the event will retain the
PERF_RECORD_MISC_MMAP_BUILD_ID flag and the build ID from the last successfully
processed module.

Will this cause perf to misattribute samples from the failing module to the
debug symbols of a completely different module?

>  		perf_record_mmap2__read_build_id(&event->mmap2, args->machine, false);
>  	} else {
>  		size = PERF_ALIGN(dso__long_name_len(dso) + 1, sizeof(u64));

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260721205746.183206-1-irogers@google.com?part=2