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

[Alexey Dobriyan <adobriyan@gmail.com>]

ELF spec doesn't require program header to be placed right after
ELF header, but build-id code very much assumes such placement:

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

and later check against PAGE_SIZE.

Returns errors for now until someone rewrites build-id parser
to be more correct.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 lib/buildid.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -73,6 +73,9 @@ static int get_build_id_32(const void *page_addr, unsigned char *build_id,
 	Elf32_Phdr *phdr;
 	int i;
 
+	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 +101,9 @@ static int get_build_id_64(const void *page_addr, unsigned char *build_id,
 	Elf64_Phdr *phdr;
 	int i;
 
+	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))