[PATCH] perf symbols: Fix return incorrect build_id size in elf_read_build_id()

[Yang Jihong]

In elf_read_build_id(), if gnu build_id is found, should return the size of
the actually copied data. If descsz is greater thanBuild_ID_SIZE,
write_buildid data access may occur.

Fixes: be96ea8ffa78 ("perf symbols: Fix issue with binaries using 16-bytes buildids (v2)")
Reported-by: Will Ochowicz <Will.Ochowicz@xxxxxxxxxxxx>
Link: https://lore.kernel.org/lkml/CWLP265MB49702F7BA3D6D8F13E4B1A719C649@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/T/
Tested-by: Will Ochowicz <Will.Ochowicz@xxxxxxxxxxxx>
Signed-off-by: Yang Jihong <yangjihong1@xxxxxxxxxx>
---
 tools/perf/util/symbol-elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 41882ae8452e..059f88eca630 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -903,7 +903,7 @@ static int elf_read_build_id(Elf *elf, void *bf, size_t size)
 				size_t sz = min(size, descsz);
 				memcpy(bf, ptr, sz);
 				memset(bf + sz, 0, size - sz);
-				err = descsz;
+				err = sz;
 				break;
 			}
 		}
-- 
2.30.GIT