exec: Move the call of prepare_binprm into search_binary_handler

The code in prepare_binary_handler needs to be run every time
search_binary_handler is called so move the call into search_binary_handler
itself to make the code simpler and easier to understand.

Link: https://lkml.kernel.org/r/87d070zrvx.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Author: ebiederm

arch/alpha/kernel/binfmt_loader.c

@@ -35,9 +35,6 @@ static int load_binary(struct linux_binprm *bprm)
 
 	bprm->file = file;
 	bprm->loader = loader;
-	retval = prepare_binprm(bprm);
-	if (retval < 0)
-		return retval;
 	return search_binary_handler(bprm);
 }
 

fs/binfmt_em86.c

@@ -91,10 +91,6 @@ static int load_em86(struct linux_binprm *bprm)
 
 	bprm->file = file;
 
-	retval = prepare_binprm(bprm);
-	if (retval < 0)
-		return retval;
-
 	return search_binary_handler(bprm);
 }
 

fs/binfmt_misc.c

@@ -221,10 +221,6 @@ static int load_misc_binary(struct linux_binprm *bprm)
 	if (fmt->flags & MISC_FMT_CREDENTIALS)
 		bprm->preserve_creds = 1;
 
-	retval = prepare_binprm(bprm);
-	if (retval < 0)
-		goto error;
-
 	retval = search_binary_handler(bprm);
 	if (retval < 0)
 		goto error;

fs/binfmt_script.c

@@ -143,9 +143,6 @@ static int load_script(struct linux_binprm *bprm)
 		return PTR_ERR(file);
 
 	bprm->file = file;
-	retval = prepare_binprm(bprm);
-	if (retval < 0)
-		return retval;
 	return search_binary_handler(bprm);
 }
 

fs/exec.c

@@ -1629,7 +1629,7 @@ static void bprm_fill_uid(struct linux_binprm *bprm)
  *
  * This may be called multiple times for binary chains (scripts for example).
  */
-int prepare_binprm(struct linux_binprm *bprm)
+static int prepare_binprm(struct linux_binprm *bprm)
 {
 	loff_t pos = 0;
 
@@ -1650,8 +1650,6 @@ int prepare_binprm(struct linux_binprm *bprm)
 	return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
 }
 
-EXPORT_SYMBOL(prepare_binprm);
-
 /*
  * Arguments are '\0' separated strings found at the location bprm->p
  * points to; chop off the first by relocating brpm->p to right after
@@ -1707,6 +1705,10 @@ int search_binary_handler(struct linux_binprm *bprm)
 	if (bprm->recursion_depth > 5)
 		return -ELOOP;
 
+	retval = prepare_binprm(bprm);
+	if (retval < 0)
+		return retval;
+
 	retval = security_bprm_check(bprm);
 	if (retval)
 		return retval;
@@ -1864,10 +1866,6 @@ static int __do_execve_file(int fd, struct filename *filename,
 	if (retval)
 		goto out;
 
-	retval = prepare_binprm(bprm);
-	if (retval < 0)
-		goto out;
-
 	retval = copy_strings_kernel(1, &bprm->filename, bprm);
 	if (retval < 0)
 		goto out;

include/linux/binfmts.h

@@ -116,7 +116,6 @@ static inline void insert_binfmt(struct linux_binfmt *fmt)
 
 extern void unregister_binfmt(struct linux_binfmt *);
 
-extern int prepare_binprm(struct linux_binprm *);
 extern int __must_check remove_arg_zero(struct linux_binprm *);
 extern int search_binary_handler(struct linux_binprm *);
 extern int begin_new_exec(struct linux_binprm * bprm);