When elf_memory is called we could get a slightly too small image that doesn't contain a full ELF header (but does contain at least the e_ident values). Require the full header before even validating the rest of the ELF header fields.
https://sourceware.org/bugzilla/show_bug.cgi?id=27076 Signed-off-by: Mark Wielaard <m...@klomp.org> --- libelf/ChangeLog | 4 ++++ libelf/elf_begin.c | 7 +++++++ 2 files changed, 11 insertions(+) diff --git a/libelf/ChangeLog b/libelf/ChangeLog index 41727fbd..a280a262 100644 --- a/libelf/ChangeLog +++ b/libelf/ChangeLog @@ -1,3 +1,7 @@ +2020-12-15 Mark Wielaard <m...@klomp.org> + + * elf_begin.c (get_shnum): Make sure the full Ehdr is available. + 2020-12-12 Dmitry V. Levin <l...@altlinux.org> * common.h: Fix spelling typo in comment. diff --git a/libelf/elf_begin.c b/libelf/elf_begin.c index 43828c9a..32648c15 100644 --- a/libelf/elf_begin.c +++ b/libelf/elf_begin.c @@ -88,6 +88,13 @@ get_shnum (void *map_address, unsigned char *e_ident, int fildes, } ehdr_mem; bool is32 = e_ident[EI_CLASS] == ELFCLASS32; + if ((is32 && maxsize < sizeof (Elf32_Ehdr)) + || (!is32 && maxsize < sizeof (Elf64_Ehdr))) + { + __libelf_seterrno (ELF_E_INVALID_ELF); + return (size_t) -1l; + } + /* Make the ELF header available. */ if (e_ident[EI_DATA] == MY_ELFDATA && (ALLOW_UNALIGNED -- 2.18.4
