lib/buildid: don't limit .note.gnu.build-id to the first page in ELF

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.

Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240829174232.3133883-8-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/lib/buildid.c b/lib/buildid.c
index 18ef558..290641d 100644 (file)
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -155,9 +155,8 @@ 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);
@@ -165,7 +164,9 @@ 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)
@@ -204,23 +205,6 @@ 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)
 {