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modules patches for 5.16-rc1

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As requested by Jessica I'm stepping in to help with modules
 maintenance. This is my first pull request to you.
 
 I've collected only two patches for modules for the 5.16-rc1 merge
 window. These patches are from Shuah Khan as she debugged some corner
 case error with modules. The error messages are improved for
 elf_validity_check(). While doing this work a corner case fix was
 spotted on validate_section_offset() due to a possible overflow bug
 on 64-bit. The impact of this fix is low given this just limits
 module section headers placed within the 32-bit boundary, and we
 obviously don't have insane module sizes. Even if a specially crafted
 module is constructed later checks would invalidate the module right
 away.
 
 I've let this sit through 0-day testing since October 15th with no
 issues found.
 
 Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
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Merge tag 'modules-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux

Pull module updates from Luis Chamberlain:
 "As requested by Jessica I'm stepping in to help with modules
  maintenance. This is my first pull request to you.

  I've collected only two patches for modules for the 5.16-rc1 merge
  window. These patches are from Shuah Khan as she debugged some corner
  case error with modules. The error messages are improved for
  elf_validity_check(). While doing this work a corner case fix was
  spotted on validate_section_offset() due to a possible overflow bug on
  64-bit. The impact of this fix is low given this just limits module
  section headers placed within the 32-bit boundary, and we obviously
  don't have insane module sizes. Even if a specially crafted module is
  constructed later checks would invalidate the module right away.

  I've let this sit through 0-day testing since October 15th with no
  issues found"

* tag 'modules-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux:
  module: change to print useful messages from elf_validity_check()
  module: fix validate_section_offset() overflow bug on 64-bit
This commit is contained in:
Linus Torvalds 2021-11-08 09:04:59 -08:00
commit 67b7e1f241
1 changed files with 58 additions and 21 deletions
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79
kernel/module.c
View File

@ -2942,7 +2942,11 @@ static int module_sig_check(struct load_info *info, int flags)
static int validate_section_offset(struct load_info *info, Elf_Shdr *shdr)
{
#if defined(CONFIG_64BIT)
unsigned long long secend;
#else
unsigned long secend;
#endif
/*
* Check for both overflow and offset/size being
@ -2967,14 +2971,29 @@ static int elf_validity_check(struct load_info *info)
Elf_Shdr *shdr, *strhdr;
int err;
if (info->len < sizeof(*(info->hdr)))
return -ENOEXEC;
if (info->len < sizeof(*(info->hdr))) {
pr_err("Invalid ELF header len %lu\n", info->len);
goto no_exec;
}
if (memcmp(info->hdr->e_ident, ELFMAG, SELFMAG) != 0
|| info->hdr->e_type != ET_REL
|| !elf_check_arch(info->hdr)
|| info->hdr->e_shentsize != sizeof(Elf_Shdr))
return -ENOEXEC;
if (memcmp(info->hdr->e_ident, ELFMAG, SELFMAG) != 0) {
pr_err("Invalid ELF header magic: != %s\n", ELFMAG);
goto no_exec;
}
if (info->hdr->e_type != ET_REL) {
pr_err("Invalid ELF header type: %u != %u\n",
info->hdr->e_type, ET_REL);
goto no_exec;
}
if (!elf_check_arch(info->hdr)) {
pr_err("Invalid architecture in ELF header: %u\n",
info->hdr->e_machine);
goto no_exec;
}
if (info->hdr->e_shentsize != sizeof(Elf_Shdr)) {
pr_err("Invalid ELF section header size\n");
goto no_exec;
}
/*
* e_shnum is 16 bits, and sizeof(Elf_Shdr) is
@ -2983,8 +3002,10 @@ static int elf_validity_check(struct load_info *info)
*/
if (info->hdr->e_shoff >= info->len
|| (info->hdr->e_shnum * sizeof(Elf_Shdr) >
info->len - info->hdr->e_shoff))
return -ENOEXEC;
info->len - info->hdr->e_shoff)) {
pr_err("Invalid ELF section header overflow\n");
goto no_exec;
}
info->sechdrs = (void *)info->hdr + info->hdr->e_shoff;
@ -2992,13 +3013,19 @@ static int elf_validity_check(struct load_info *info)
* Verify if the section name table index is valid.
*/
if (info->hdr->e_shstrndx == SHN_UNDEF
|| info->hdr->e_shstrndx >= info->hdr->e_shnum)
return -ENOEXEC;
|| info->hdr->e_shstrndx >= info->hdr->e_shnum) {
pr_err("Invalid ELF section name index: %d || e_shstrndx (%d) >= e_shnum (%d)\n",
info->hdr->e_shstrndx, info->hdr->e_shstrndx,
info->hdr->e_shnum);
goto no_exec;
}
strhdr = &info->sechdrs[info->hdr->e_shstrndx];
err = validate_section_offset(info, strhdr);
if (err < 0)
if (err < 0) {
pr_err("Invalid ELF section hdr(type %u)\n", strhdr->sh_type);
return err;
}
/*
* The section name table must be NUL-terminated, as required
@ -3006,8 +3033,10 @@ static int elf_validity_check(struct load_info *info)
* strings in the section safe.
*/
info->secstrings = (void *)info->hdr + strhdr->sh_offset;
if (info->secstrings[strhdr->sh_size - 1] != '\0')
return -ENOEXEC;
if (info->secstrings[strhdr->sh_size - 1] != '\0') {
pr_err("ELF Spec violation: section name table isn't null terminated\n");
goto no_exec;
}
/*
* The code assumes that section 0 has a length of zero and
@ -3015,8 +3044,11 @@ static int elf_validity_check(struct load_info *info)
*/
if (info->sechdrs[0].sh_type != SHT_NULL
|| info->sechdrs[0].sh_size != 0
|| info->sechdrs[0].sh_addr != 0)
return -ENOEXEC;
|| info->sechdrs[0].sh_addr != 0) {
pr_err("ELF Spec violation: section 0 type(%d)!=SH_NULL or non-zero len or addr\n",
info->sechdrs[0].sh_type);
goto no_exec;
}
for (i = 1; i < info->hdr->e_shnum; i++) {
shdr = &info->sechdrs[i];
@ -3026,8 +3058,12 @@ static int elf_validity_check(struct load_info *info)
continue;
case SHT_SYMTAB:
if (shdr->sh_link == SHN_UNDEF
|| shdr->sh_link >= info->hdr->e_shnum)
return -ENOEXEC;
|| shdr->sh_link >= info->hdr->e_shnum) {
pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= hdr->e_shnum(%d)\n",
shdr->sh_link, shdr->sh_link,
info->hdr->e_shnum);
goto no_exec;
}
fallthrough;
default:
err = validate_section_offset(info, shdr);
@ -3049,6 +3085,9 @@ static int elf_validity_check(struct load_info *info)
}
return 0;
no_exec:
return -ENOEXEC;
}
#define COPY_CHUNK_SIZE (16*PAGE_SIZE)
@ -3940,10 +3979,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
* sections.
*/
err = elf_validity_check(info);
if (err) {
pr_err("Module has invalid ELF structures\n");
if (err)
goto free_copy;
}
/*
* Everything checks out, so set up the section info