[PATCH v2] build-id: require program headers to be right after ELF header

From: Alexey Dobriyan
Date: Fri Jun 21 2024 - 14:39:47 EST


Neither ELF spec not ELF loader require program header to be placed
right after ELF header, but build-id code very much assumes such placement:

See

find_get_page(vma->vm_file->f_mapping, 0);

line and checks against PAGE_SIZE.

Returns errors for now until someone rewrites build-id parser
to be more inline with load_elf_binary().

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---

lib/buildid.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -73,6 +73,13 @@ static int get_build_id_32(const void *page_addr, unsigned char *build_id,
Elf32_Phdr *phdr;
int i;

+ /*
+ * FIXME
+ * Neither ELF spec nor ELF loader require that program headers
+ * start immediately after ELF header.
+ */
+ if (ehdr->e_phoff != sizeof(Elf32_Ehdr))
+ return -EINVAL;
/* only supports phdr that fits in one page */
if (ehdr->e_phnum >
(PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
@@ -98,6 +105,13 @@ static int get_build_id_64(const void *page_addr, unsigned char *build_id,
Elf64_Phdr *phdr;
int i;

+ /*
+ * FIXME
+ * Neither ELF spec nor ELF loader require that program headers
+ * start immediately after ELF header.
+ */
+ if (ehdr->e_phoff != sizeof(Elf64_Ehdr))
+ return -EINVAL;
/* only supports phdr that fits in one page */
if (ehdr->e_phnum >
(PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))