From d08572f7c9692c335afdb6f8dde48d77731209c3 Mon Sep 17 00:00:00 2001 From: Mark Wielaard Date: Fri, 28 Sep 2018 10:45:56 +0800 Subject: [PATCH 2/2] libelf: Return error if elf_compress_gnu is used on SHF_COMPRESSED section. Compressing a section that is already compressed is fine, but useless. But it isn't possible to gnu compress (or decompress) a SHF_COMPRESSED section since there is no state kept that would tell if the section was first GNU compressed or first gabi compressed. Calling elf_compress_gnu on a section and then calling elf_compress on it to decompress it twice could cause a crash (the other way around is fine). Just disallow it. https://sourceware.org/bugzilla/show_bug.cgi?id=23528 Signed-off-by: Mark Wielaard Upstream-Status: Backport [https://sourceware.org/git/?p=elfutils.git;a=commit;h=56b18521fb8d46d40fc090c0de9d11a08bc982fa] CVE: CVE-2018-16402 Signed-off-by: Hongxu Jia --- libelf/elf_compress_gnu.c | 4 +++- libelf/libelf.h | 5 +++++ 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/libelf/elf_compress_gnu.c b/libelf/elf_compress_gnu.c index c35dc39..dfa7c57 100644 --- a/libelf/elf_compress_gnu.c +++ b/libelf/elf_compress_gnu.c @@ -80,7 +80,9 @@ elf_compress_gnu (Elf_Scn *scn, int inflate, unsigned int flags) sh_addralign = shdr->sh_addralign; } - if ((sh_flags & SHF_ALLOC) != 0) + /* Allocated sections, or sections that are already are compressed + cannot (also) be GNU compressed. */ + if ((sh_flags & SHF_ALLOC) != 0 || (sh_flags & SHF_COMPRESSED)) { __libelf_seterrno (ELF_E_INVALID_SECTION_FLAGS); return -1; diff --git a/libelf/libelf.h b/libelf/libelf.h index 547c0f5..fa568f7 100644 --- a/libelf/libelf.h +++ b/libelf/libelf.h @@ -366,6 +366,11 @@ extern Elf64_Chdr *elf64_getchdr (Elf_Scn *__scn); It is an error to request compression for a section that already has SHF_COMPRESSED set, or (for elf_compress) to request decompression for an section that doesn't have SHF_COMPRESSED set. + If a section has SHF_COMPRESSED set then calling elf_compress_gnu + will result in an error. The section has to be decompressed first + using elf_compress. Calling elf_compress on a section compressed + with elf_compress_gnu is fine, but probably useless. + It is always an error to call these functions on SHT_NOBITS sections or if the section has the SHF_ALLOC flag set. elf_compress_gnu will not check whether the section name starts -- 2.7.4