Current code assumption is that program (segment) headers are following
ELF header immediately. This is a common case, but is not guaranteed. So
take into account e_phoff field of the ELF header when accessing program
headers.
Reported-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
lib/buildid.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/lib/buildid.c b/lib/buildid.c
index 1442a2483a8b..ce48ffab4111 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -206,7 +206,7 @@ static int get_build_id_32(struct freader *r, unsigned char *build_id, __u32 *si
{
const Elf32_Ehdr *ehdr;
const Elf32_Phdr *phdr;
- __u32 phnum, i;
+ __u32 phnum, phoff, i;
ehdr = freader_fetch(r, 0, sizeof(Elf32_Ehdr));
if (!ehdr)
@@ -214,13 +214,14 @@ static int get_build_id_32(struct freader *r, unsigned char *build_id, __u32 *si
/* subsequent freader_fetch() calls invalidate pointers, so remember locally */
phnum = ehdr->e_phnum;
+ phoff = READ_ONCE(ehdr->e_phoff);
/* only supports phdr that fits in one page */
if (phnum > (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
return -EINVAL;
for (i = 0; i < phnum; ++i) {
- phdr = freader_fetch(r, i * sizeof(Elf32_Phdr), sizeof(Elf32_Phdr));
+ phdr = freader_fetch(r, phoff + i * sizeof(Elf32_Phdr), sizeof(Elf32_Phdr));
if (!phdr)
return r->err;
@@ -237,6 +238,7 @@ static int get_build_id_64(struct freader *r, unsigned char *build_id, __u32 *si
const Elf64_Ehdr *ehdr;
const Elf64_Phdr *phdr;
__u32 phnum, i;
+ __u64 phoff;
ehdr = freader_fetch(r, 0, sizeof(Elf64_Ehdr));
if (!ehdr)
@@ -244,13 +246,14 @@ static int get_build_id_64(struct freader *r, unsigned char *build_id, __u32 *si
/* subsequent freader_fetch() calls invalidate pointers, so remember locally */
phnum = ehdr->e_phnum;
+ phoff = READ_ONCE(ehdr->e_phoff);
/* only supports phdr that fits in one page */
if (phnum > (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
return -EINVAL;
for (i = 0; i < phnum; ++i) {
- phdr = freader_fetch(r, i * sizeof(Elf64_Phdr), sizeof(Elf64_Phdr));
+ phdr = freader_fetch(r, phoff + i * sizeof(Elf64_Phdr), sizeof(Elf64_Phdr));
if (!phdr)
return r->err;
--
2.43.0
