[PATCH v5 bpf-next 07/10] lib/buildid: don't limit .note.gnu.build-id to the first page in ELF

Andrii Nakryiko
2024-08-13T00:30:05Z

With freader we don't need to restrict ourselves to a single page, so
let's allow ELF notes to be at any valid position with the file.

We also merge parse_build_id() and parse_build_id_buf() as now the only
difference between them is note offset overflow, which makes sense to
check in all situations.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
lib/buildid.c | 26 +++++---------------------
1 file changed, 5 insertions(+), 21 deletions(-)

diff --git a/lib/buildid.c b/lib/buildid.c
index e78bef392cfd..3f7a588f7fd2 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -153,9 +153,8 @@ static void freader_cleanup(struct freader *r)
* 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
* identical.
*/
-static int parse_build_id_buf(struct freader *r,
- unsigned char *build_id, __u32 *size,
- loff_t note_off, Elf32_Word note_size)
+static int parse_build_id(struct freader *r, unsigned char *build_id, __u32 *size,
+ loff_t note_off, Elf32_Word note_size)
{
const char note_name[] = "GNU";
const size_t note_name_sz = sizeof(note_name);
@@ -163,7 +162,9 @@ static int parse_build_id_buf(struct freader *r,
const Elf32_Nhdr *nhdr;
const char *data;

- note_end = note_off + note_size;
+ if (check_add_overflow(note_off, note_size, &note_end))
+ return -EINVAL;
+
while (note_end - note_off > sizeof(Elf32_Nhdr) + note_name_sz) {
nhdr = freader_fetch(r, note_off, sizeof(Elf32_Nhdr) + note_name_sz);
if (!nhdr)
@@ -202,23 +203,6 @@ static int parse_build_id_buf(struct freader *r,
return -EINVAL;
}

-static inline int parse_build_id(struct freader *r,
- unsigned char *build_id,
- __u32 *size,
- loff_t note_start_off,
- Elf32_Word note_size)
-{
- /* check for overflow */
- if (note_start_off + note_size < note_start_off)
- return -EINVAL;
-
- /* only supports note that fits in the first page */
- if (note_start_off + note_size > PAGE_SIZE)
- return -EINVAL;
-
- return parse_build_id_buf(r, build_id, size, note_start_off, note_size);
-}
-
/* Parse build ID from 32-bit ELF */
static int get_build_id_32(struct freader *r, unsigned char *build_id, __u32 *size)
{
--
2.43.5