From: Alan Modra <amodra@gmail.com>
To: binutils@sourceware.org
Subject: SHT_RELR sh_link and sh_info
Date: Tue, 23 Aug 2022 21:26:57 +0930 [thread overview]
Message-ID: <YwTAiYWy3V7e16EF@squeak.grove.modra.org> (raw)
I don't think it makes any sense for a SHT_RELR section to specify a
symbol table with sh_link. SHT_RELR relocations don't use symbols.
There is no real need to specify sh_info either, SHT_RELR is not for
relocatable object files. Anyway, fuzzers of course don't restrict
themselves to even half-sensible objects. So they found a hole in
objcopy using a non-alloc SHT_RELR in an ET_EXEC. In that case BFD
set up the SHT_RELR section as if it were a SHT_REL against the
sh_info target section. When it came to reading in the target section
relocs, the count was horribly wrong which caused a buffer overflow.
* elf.c (bfd_section_from_shdr <SHT_RELR>): Always just make a
normal section, don't treat it as a reloc section.
diff --git a/bfd/elf.c b/bfd/elf.c
index f186a2cffe9..8aba36acb3c 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -2409,6 +2409,7 @@ bfd_section_from_shdr (bfd *abfd, unsigned int shindex)
its sh_link points to the null section. */
if (((abfd->flags & (DYNAMIC | EXEC_P)) != 0
&& (hdr->sh_flags & SHF_ALLOC) != 0)
+ || hdr->sh_type == SHT_RELR
|| hdr->sh_link == SHN_UNDEF
|| hdr->sh_link != elf_onesymtab (abfd)
|| hdr->sh_info == SHN_UNDEF
--
Alan Modra
Australia Development Lab, IBM
reply other threads:[~2022-08-23 11:57 UTC|newest]
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