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

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Date: Fri, 21 Jun 2024 21:39:33 +0300
From: Alexey Dobriyan <adobriyan@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>
Subject: [PATCH v2] build-id: require program headers to be right after ELF
 header

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@...il.com>
---

 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))