The build_id parsing functions calculate a filename length from the
event header size and read directly into a stack buffer of PATH_MAX
bytes without bounds checking. A malformed perf.data file with a
crafted header.size can cause the length to be negative or exceed
PATH_MAX, resulting in a stack buffer overflow.

Add bounds checking for the filename length in both
perf_header__read_build_ids() and the ABI quirk variant. Print a
warning message when invalid length is detected.

Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
---
v3:
 - Fix printf format specifier: %d -> %zd for ssize_t (Sashiko)
v2:
 - Add warning message when invalid filename length detected
---
 tools/perf/util/header.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 9142a8ba4019..9ffc0f4ca6d1 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2545,6 +2545,11 @@ static int perf_header__read_build_ids_abi_quirk(struct perf_header *header,
 			perf_event_header__bswap(&old_bev.header);
 
 		len = old_bev.header.size - sizeof(old_bev);
+		if (len < 0 || len >= PATH_MAX) {
+			pr_warning("invalid build_id filename length %zd\n", len);
+			return -1;
+		}
+
 		if (readn(input, filename, len) != len)
 			return -1;
 
@@ -2587,6 +2592,11 @@ static int perf_header__read_build_ids(struct perf_header *header,
 			perf_event_header__bswap(&bev.header);
 
 		len = bev.header.size - sizeof(bev);
+		if (len < 0 || len >= PATH_MAX) {
+			pr_warning("invalid build_id filename length %zd\n", len);
+			goto out;
+		}
+
 		if (readn(input, filename, len) != len)
 			goto out;
 		/*
-- 
2.52.0

On Fri, 03 Apr 2026 01:04:10 +0900, SeungJu Cheon wrote:
> The build_id parsing functions calculate a filename length from the
> event header size and read directly into a stack buffer of PATH_MAX
> bytes without bounds checking. A malformed perf.data file with a
> crafted header.size can cause the length to be negative or exceed
> PATH_MAX, resulting in a stack buffer overflow.
> 
> Add bounds checking for the filename length in both
> perf_header__read_build_ids() and the ABI quirk variant. Print a
> warning message when invalid length is detected.
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung