diff --git a/kernel/module.c b/kernel/module.c
index 805c49d1b86da29eafd8fd8cd9a9883c98c02701..1e5aad8123104b79b0dc7cf5a3cbf151b23f1671 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2981,7 +2981,7 @@ static int module_sig_check(struct load_info *info, int flags)
}
if (is_module_sig_enforced()) {
- pr_notice("%s: loading of %s is rejected\n", info->name, reason);
+ pr_notice("Loading of %s is rejected\n", reason);
return -EKEYREJECTED;
}
@@ -2994,9 +2994,33 @@ static int module_sig_check(struct load_info *info, int flags)
}
#endif /* !CONFIG_MODULE_SIG */
-/* Sanity checks against invalid binaries, wrong arch, weird elf version. */
-static int elf_header_check(struct load_info *info)
+static int validate_section_offset(struct load_info *info, Elf_Shdr *shdr)
{
+ unsigned long secend;
+
+ /*
+ * Check for both overflow and offset/size being
+ * too large.
+ */
+ secend = shdr->sh_offset + shdr->sh_size;
+ if (secend < shdr->sh_offset || secend > info->len)
+ return -ENOEXEC;
+
+ return 0;
+}
+
+/*
+ * Sanity checks against invalid binaries, wrong arch, weird elf version.
+ *
+ * Also do basic validity checks against section offsets and sizes, the
+ * section name string table, and the indices used for it (sh_name).
+ */
+static int elf_validity_check(struct load_info *info)
+{
+ unsigned int i;
+ Elf_Shdr *shdr, *strhdr;
+ int err;
+
if (info->len < sizeof(*(info->hdr)))
return -ENOEXEC;
@@ -3006,11 +3030,78 @@ static int elf_header_check(struct load_info *info)
|| info->hdr->e_shentsize != sizeof(Elf_Shdr))
return -ENOEXEC;
+ /*
+ * e_shnum is 16 bits, and sizeof(Elf_Shdr) is
+ * known and small. So e_shnum * sizeof(Elf_Shdr)
+ * will not overflow unsigned long on any platform.
+ */
if (info->hdr->e_shoff >= info->len
|| (info->hdr->e_shnum * sizeof(Elf_Shdr) >
info->len - info->hdr->e_shoff))
return -ENOEXEC;
+ info->sechdrs = (void *)info->hdr + info->hdr->e_shoff;
+
+ /*
+ * 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;
+
+ strhdr = &info->sechdrs[info->hdr->e_shstrndx];
+ err = validate_section_offset(info, strhdr);
+ if (err < 0)
+ return err;
+
+ /*
+ * The section name table must be NUL-terminated, as required
+ * by the spec. This makes strcmp and pr_* calls that access
+ * strings in the section safe.
+ */
+ info->secstrings = (void *)info->hdr + strhdr->sh_offset;
+ if (info->secstrings[strhdr->sh_size - 1] != '\0')
+ return -ENOEXEC;
+
+ /*
+ * The code assumes that section 0 has a length of zero and
+ * an addr of zero, so check for it.
+ */
+ if (info->sechdrs[0].sh_type != SHT_NULL
+ || info->sechdrs[0].sh_size != 0
+ || info->sechdrs[0].sh_addr != 0)
+ return -ENOEXEC;
+
+ for (i = 1; i < info->hdr->e_shnum; i++) {
+ shdr = &info->sechdrs[i];
+ switch (shdr->sh_type) {
+ case SHT_NULL:
+ case SHT_NOBITS:
+ continue;
+ case SHT_SYMTAB:
+ if (shdr->sh_link == SHN_UNDEF
+ || shdr->sh_link >= info->hdr->e_shnum)
+ return -ENOEXEC;
+ fallthrough;
+ default:
+ err = validate_section_offset(info, shdr);
+ if (err < 0) {
+ pr_err("Invalid ELF section in module (section %u type %u)\n",
+ i, shdr->sh_type);
+ return err;
+ }
+
+ if (shdr->sh_flags & SHF_ALLOC) {
+ if (shdr->sh_name >= strhdr->sh_size) {
+ pr_err("Invalid ELF section name in module (section %u type %u)\n",
+ i, shdr->sh_type);
+ return -ENOEXEC;
+ }
+ }
+ break;
+ }
+ }
+
return 0;
}
@@ -3112,11 +3203,6 @@ static int rewrite_section_headers(struct load_info *info, int flags)
for (i = 1; i < info->hdr->e_shnum; i++) {
Elf_Shdr *shdr = &info->sechdrs[i];
- if (shdr->sh_type != SHT_NOBITS
- && info->len < shdr->sh_offset + shdr->sh_size) {
- pr_err("Module len %lu truncated\n", info->len);
- return -ENOEXEC;
- }
/*
* Mark all sections sh_addr with their address in the
@@ -3150,11 +3236,6 @@ static int setup_load_info(struct load_info *info, int flags)
{
unsigned int i;
- /* Set up the convenience variables */
- info->sechdrs = (void *)info->hdr + info->hdr->e_shoff;
- info->secstrings = (void *)info->hdr
- + info->sechdrs[info->hdr->e_shstrndx].sh_offset;
-
/* Try to find a name early so we can log errors with a module name */
info->index.info = find_sec(info, ".modinfo");
if (info->index.info)
@@ -3911,26 +3992,50 @@ static int load_module(struct load_info *info, const char __user *uargs,
long err = 0;
char *after_dashes;
- err = elf_header_check(info);
+ /*
+ * Do the signature check (if any) first. All that
+ * the signature check needs is info->len, it does
+ * not need any of the section info. That can be
+ * set up later. This will minimize the chances
+ * of a corrupt module causing problems before
+ * we even get to the signature check.
+ *
+ * The check will also adjust info->len by stripping
+ * off the sig length at the end of the module, making
+ * checks against info->len more correct.
+ */
+ err = module_sig_check(info, flags);
+ if (err)
+ goto free_copy;
+
+ /*
+ * Do basic sanity checks against the ELF header and
+ * sections.
+ */
+ err = elf_validity_check(info);
if (err) {
- pr_err("Module has invalid ELF header\n");
+ pr_err("Module has invalid ELF structures\n");
goto free_copy;
}
+ /*
+ * Everything checks out, so set up the section info
+ * in the info structure.
+ */
err = setup_load_info(info, flags);
if (err)
goto free_copy;
+ /*
+ * Now that we know we have the correct module name, check
+ * if it's blacklisted.
+ */
if (blacklisted(info->name)) {
err = -EPERM;
pr_err("Module %s is blacklisted\n", info->name);
goto free_copy;
}
- err = module_sig_check(info, flags);
- if (err)
- goto free_copy;
-
err = rewrite_section_headers(info, flags);
if (err)
goto free_copy;
diff --git a/kernel/module_signature.c b/kernel/module_signature.c
index 4224a1086b7d8b78c813ec7990c06a9b802c5370..00132d12487cd75d59f865f9b530af7ed969c48a 100644
--- a/kernel/module_signature.c
+++ b/kernel/module_signature.c
@@ -25,7 +25,7 @@ int mod_check_sig(const struct module_signature *ms, size_t file_len,
return -EBADMSG;
if (ms->id_type != PKEY_ID_PKCS7) {
- pr_err("%s: Module is not signed with expected PKCS#7 message\n",
+ pr_err("%s: not signed with expected PKCS#7 message\n",
name);
return -ENOPKG;
}
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 9d9fc678c91d6668103faced46bc2a5f47baab49..8723ae70ea1fe4029a52587032f47dede603096d 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -30,7 +30,7 @@ int mod_verify_sig(const void *mod, struct load_info *info)
memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
- ret = mod_check_sig(&ms, modlen, info->name);
+ ret = mod_check_sig(&ms, modlen, "module");
if (ret)
return ret;