From 33035f7dd4e49f3f117e70c5e36c8c1ae88d37f2 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Sun, 7 Jun 2026 21:03:13 -0300 Subject: [PATCH] perf pmu: Fix perf_pmu__parse_scale/unit() OOB access on empty sysfs file MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit perf_pmu__parse_scale() reads a PMU scale file then accesses scale[sret - 1] to strip a trailing newline. Only sret < 0 is guarded, so an empty file (sret == 0) causes scale[-1] — a stack buffer underflow that reads and potentially writes out of bounds. perf_pmu__parse_unit() has the same pattern: alias->unit[sret - 1] with sret == 0 accesses the byte before the struct member, which may corrupt the adjacent pmu_name pointer field. Change both guards from sret < 0 to sret <= 0 so that empty files are treated as read errors. Fixes: 410136f5dd96b601 ("tools/perf/stat: Add event unit and scale support") Reported-by: sashiko-bot Cc: Stephane Eranian Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/pmu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c index f588cce601941..a550f030b85df 100644 --- a/tools/perf/util/pmu.c +++ b/tools/perf/util/pmu.c @@ -314,7 +314,7 @@ static int perf_pmu__parse_scale(struct perf_pmu *pmu, struct perf_pmu_alias *al goto error; sret = read(fd, scale, sizeof(scale)-1); - if (sret < 0) + if (sret <= 0) goto error; if (scale[sret - 1] == '\n') @@ -346,7 +346,7 @@ static int perf_pmu__parse_unit(struct perf_pmu *pmu, struct perf_pmu_alias *ali return -1; sret = read(fd, alias->unit, UNIT_MAX_LEN); - if (sret < 0) + if (sret <= 0) goto error; close(fd); -- 2.47.3