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