Commit d2e4d05c authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

modpost: fix potential segmentation fault for addend_i386_rel() 



This may not be a practical problem, but the second pass of ARCH=i386
modpost causes segmentation fault if the -s option is not passed.

    MODPOST 12 modules
  Segmentation fault (core dumped)
  make[2]: *** [scripts/Makefile.modpost:94: __modpost] Error 139
  make[1]: *** [Makefile:1339: modules] Error 2
  make[1]: *** Waiting for unfinished jobs....

The segmentation fault occurs when section_rel() is called for vmlinux,
which is untested in regular builds. The cause of the problem is
reloc_location() returning a wrong pointer for ET_EXEC object type.
In this case, you need to subtract sechdr->sh_addr, otherwise it would
get access beyond the mmap'ed memory.

Add sym_get_data_by_offset() helper to avoid code duplication.

Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
parent e9e81b63

scripts/mod/modpost.c

+9 −9
Original line number Diff line number Diff line
@@ -300,19 +300,23 @@ static const char *sec_name(struct elf_info *elf, int secindex) 
	return sech_name(elf, &elf->sechdrs[secindex]);

}



static void *sym_get_data(const struct elf_info *info, const Elf_Sym *sym)

static void *sym_get_data_by_offset(const struct elf_info *info,

				    unsigned int secindex, unsigned long offset)

{

	unsigned int secindex = get_secindex(info, sym);

	Elf_Shdr *sechdr = &info->sechdrs[secindex];

	unsigned long offset;



	offset = sym->st_value;

	if (info->hdr->e_type != ET_REL)

		offset -= sechdr->sh_addr;



	return (void *)info->hdr + sechdr->sh_offset + offset;

}



static void *sym_get_data(const struct elf_info *info, const Elf_Sym *sym)

{

	return sym_get_data_by_offset(info, get_secindex(info, sym),

				      sym->st_value);

}



#define strstarts(str, prefix) (strncmp(str, prefix, strlen(prefix)) == 0)



static enum export export_from_secname(struct elf_info *elf, unsigned int sec)
@@ -1752,11 +1756,7 @@ static void check_section_mismatch(const char *modname, struct elf_info *elf, 
static unsigned int *reloc_location(struct elf_info *elf,

				    Elf_Shdr *sechdr, Elf_Rela *r)

{

	Elf_Shdr *sechdrs = elf->sechdrs;

	int section = sechdr->sh_info;



	return (void *)elf->hdr + sechdrs[section].sh_offset +

		r->r_offset;

	return sym_get_data_by_offset(elf, sechdr->sh_info, r->r_offset);

}



static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)

CRA Git | Maintained and supported by SUSTech CRA and CCSE