[PATCH v5 07/16] module: Factor out elf_validity_cache_index_sym

[Matthew Maurer]

Centralize symbol table detection and property validation.

Signed-off-by: Matthew Maurer <mmau...@google.com>
---
 kernel/module/main.c | 73 ++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 29 deletions(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index ec638187ffcf..6be58b0a6468 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1980,6 +1980,39 @@ static int elf_validity_cache_index_mod(struct load_info 
*info)
        return 0;
 }
 
+/**
+ * elf_validity_cache_index_sym() - Validate and cache symtab index
+ * @info: Load info to cache symtab index in.
+ *        Must have &load_info->sechdrs and &load_info->secstrings populated.
+ *
+ * Checks that there is exactly one symbol table, then caches its index in
+ * &load_info->index.sym.
+ *
+ * Return: %0 if valid, %-ENOEXEC on failure.
+ */
+static int elf_validity_cache_index_sym(struct load_info *info)
+{
+       unsigned int sym_idx;
+       unsigned int num_sym_secs = 0;
+       int i;
+
+       for (i = 1; i < info->hdr->e_shnum; i++) {
+               if (info->sechdrs[i].sh_type == SHT_SYMTAB) {
+                       num_sym_secs++;
+                       sym_idx = i;
+               }
+       }
+
+       if (num_sym_secs != 1) {
+               pr_warn("%s: module has no symbols (stripped?)\n",
+                       info->name ?: "(missing .modinfo section or name 
field)");
+               return -ENOEXEC;
+       }
+
+       info->index.sym = sym_idx;
+
+       return 0;
+}
 
 /*
  * Check userspace passed ELF module against our expectations, and cache
@@ -2003,10 +2036,8 @@ static int elf_validity_cache_index_mod(struct load_info 
*info)
  */
 static int elf_validity_cache_copy(struct load_info *info, int flags)
 {
-       unsigned int i;
-       Elf_Shdr *shdr;
        int err;
-       unsigned int num_sym_secs = 0, sym_idx;
+       int str_idx;
 
        err = elf_validity_cache_sechdrs(info);
        if (err < 0)
@@ -2018,34 +2049,21 @@ static int elf_validity_cache_copy(struct load_info 
*info, int flags)
        if (err < 0)
                return err;
        err = elf_validity_cache_index_mod(info);
+       if (err < 0)
+               return err;
+       err = elf_validity_cache_index_sym(info);
        if (err < 0)
                return err;
 
-       for (i = 1; i < info->hdr->e_shnum; i++) {
-               shdr = &info->sechdrs[i];
-               if (shdr->sh_type == SHT_SYMTAB) {
-                       if (shdr->sh_link == SHN_UNDEF
-                           || 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;
-                       }
-                       num_sym_secs++;
-                       sym_idx = i;
-               }
-       }
-
-       if (num_sym_secs != 1) {
-               pr_warn("%s: module has no symbols (stripped?)\n",
-                       info->name ?: "(missing .modinfo section or name 
field)");
-               goto no_exec;
+       str_idx = info->sechdrs[info->index.sym].sh_link;
+       if (str_idx == SHN_UNDEF || str_idx >= info->hdr->e_shnum) {
+               pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= 
hdr->e_shnum(%d)\n",
+                               str_idx, str_idx, info->hdr->e_shnum);
+               return -ENOEXEC;
        }
 
-       /* Sets internal symbols and strings. */
-       info->index.sym = sym_idx;
-       shdr = &info->sechdrs[sym_idx];
-       info->index.str = shdr->sh_link;
+       /* Sets internal strings. */
+       info->index.str = str_idx;
        info->strtab = (char *)info->hdr + 
info->sechdrs[info->index.str].sh_offset;
 
        /* This is temporary: point mod into copy of data. */
@@ -2066,9 +2084,6 @@ static int elf_validity_cache_copy(struct load_info 
*info, int flags)
        info->index.pcpu = find_pcpusec(info);
 
        return 0;
-
-no_exec:
-       return -ENOEXEC;
 }
 
 #define COPY_CHUNK_SIZE (16*PAGE_SIZE)
-- 
2.46.1.824.gd892dcdcdd-goog