module: refactor load_module part 3

Extract out the allocation and copying in from userspace, and the
first set of modinfo checks.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 75 insertions, 47 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 19ddcb0dba36..d8faf35cba84 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1803,7 +1803,7 @@ static char *next_string(char *string, unsigned long *secsize)
         return string;
 }
 
-static char *get_modinfo(Elf_Shdr *sechdrs,
+static char *get_modinfo(const Elf_Shdr *sechdrs,
                          unsigned int info,
                          const char *tag)
 {
@@ -2109,6 +2109,73 @@ static inline void kmemleak_load_module(struct module *mod, Elf_Ehdr *hdr,
 }
 #endif
 
+static int copy_and_check(Elf_Ehdr **hdrp,
+                          const void __user *umod, unsigned long len)
+{
+        int err;
+        Elf_Ehdr *hdr;
+
+        if (len < sizeof(*hdr))
+                return -ENOEXEC;
+
+        /* Suck in entire file: we'll want most of it. */
+        /* vmalloc barfs on "unusual" numbers.  Check here */
+        if (len > 64 * 1024 * 1024 || (hdr = *hdrp = vmalloc(len)) == NULL)
+                return -ENOMEM;
+
+        if (copy_from_user(hdr, umod, len) != 0) {
+                err = -EFAULT;
+                goto free_hdr;
+        }
+
+        /* Sanity checks against insmoding binaries or wrong arch,
+           weird elf version */
+        if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0
+            || hdr->e_type != ET_REL
+            || !elf_check_arch(hdr)
+            || hdr->e_shentsize != sizeof(Elf_Shdr)) {
+                err = -ENOEXEC;
+                goto free_hdr;
+        }
+
+        if (len < hdr->e_shoff + hdr->e_shnum * sizeof(Elf_Shdr)) {
+                err = -ENOEXEC;
+                goto free_hdr;
+        }
+        return 0;
+
+free_hdr:
+        vfree(hdr);
+        return err;
+}
+
+static int check_modinfo(struct module *mod,
+                         const Elf_Shdr *sechdrs,
+                         unsigned int infoindex, unsigned int versindex)
+{
+        const char *modmagic = get_modinfo(sechdrs, infoindex, "vermagic");
+        int err;
+
+        /* This is allowed: modprobe --force will invalidate it. */
+        if (!modmagic) {
+                err = try_to_force_load(mod, "bad vermagic");
+                if (err)
+                        return err;
+        } else if (!same_magic(modmagic, vermagic, versindex)) {
+                printk(KERN_ERR "%s: version magic '%s' should be '%s'\n",
+                       mod->name, modmagic, vermagic);
+                return -ENOEXEC;
+        }
+
+        if (get_modinfo(sechdrs, infoindex, "staging")) {
+                add_taint_module(mod, TAINT_CRAP);
+                printk(KERN_WARNING "%s: module is from the staging directory,"
+                       " the quality is unknown, you have been warned.\n",
+                       mod->name);
+        }
+        return 0;
+}
+
 static void find_module_sections(struct module *mod, Elf_Ehdr *hdr,
                                  Elf_Shdr *sechdrs, const char *secstrings)
 {
@@ -2246,14 +2313,13 @@ static noinline struct module *load_module(void __user *umod,
 {
         Elf_Ehdr *hdr;
         Elf_Shdr *sechdrs;
-        char *secstrings, *args, *modmagic, *strtab = NULL;
-        char *staging;
+        char *secstrings, *args, *strtab = NULL;
         unsigned int i;
         unsigned int symindex = 0;
         unsigned int strindex = 0;
         unsigned int modindex, versindex, infoindex, pcpuindex;
         struct module *mod;
-        long err = 0;
+        long err;
         unsigned long symoffs, stroffs, *strmap;
         void __percpu *percpu;
         struct _ddebug *debug = NULL;
@@ -2263,31 +2329,10 @@ static noinline struct module *load_module(void __user *umod,
 
         DEBUGP("load_module: umod=%p, len=%lu, uargs=%p\n",
                umod, len, uargs);
-        if (len < sizeof(*hdr))
-                return ERR_PTR(-ENOEXEC);
-
-        /* Suck in entire file: we'll want most of it. */
-        /* vmalloc barfs on "unusual" numbers.  Check here */
-        if (len > 64 * 1024 * 1024 || (hdr = vmalloc(len)) == NULL)
-                return ERR_PTR(-ENOMEM);
-
-        if (copy_from_user(hdr, umod, len) != 0) {
-                err = -EFAULT;
-                goto free_hdr;
-        }
-
-        /* Sanity checks against insmoding binaries or wrong arch,
-           weird elf version */
-        if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0
-            || hdr->e_type != ET_REL
-            || !elf_check_arch(hdr)
-            || hdr->e_shentsize != sizeof(*sechdrs)) {
-                err = -ENOEXEC;
-                goto free_hdr;
-        }
 
-        if (len < hdr->e_shoff + hdr->e_shnum * sizeof(Elf_Shdr))
-                goto truncated;
+        err = copy_and_check(&hdr, umod, len);
+        if (err)
+                return ERR_PTR(err);
 
         /* Convenience variables */
         sechdrs = (void *)hdr + hdr->e_shoff;
@@ -2347,26 +2392,9 @@ static noinline struct module *load_module(void __user *umod,
                 goto free_hdr;
         }
 
-        modmagic = get_modinfo(sechdrs, infoindex, "vermagic");
-        /* This is allowed: modprobe --force will invalidate it. */
-        if (!modmagic) {
-                err = try_to_force_load(mod, "bad vermagic");
-                if (err)
-                        goto free_hdr;
-        } else if (!same_magic(modmagic, vermagic, versindex)) {
-                printk(KERN_ERR "%s: version magic '%s' should be '%s'\n",
-                       mod->name, modmagic, vermagic);
-                err = -ENOEXEC;
+        err = check_modinfo(mod, sechdrs, infoindex, versindex);
+        if (err)
                 goto free_hdr;
-        }
-
-        staging = get_modinfo(sechdrs, infoindex, "staging");
-        if (staging) {
-                add_taint_module(mod, TAINT_CRAP);
-                printk(KERN_WARNING "%s: module is from the staging directory,"
-                       " the quality is unknown, you have been warned.\n",
-                       mod->name);
-        }
 
         /* Now copy in args */
         args = strndup_user(uargs, ~0UL >> 1);