exec: kill "int depth" in search_binary_handler()

Nobody except search_binary_handler() should touch ->recursion_depth, "int
depth" buys nothing but complicates the code, kill it.

Probably we should also kill "fn" and the !NULL check, ->load_binary
should be always defined.  And it can not go away after read_unlock() or
this code is buggy anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Zach Levis <zml@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 5 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 4d95b47..b6e35ec 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1370,12 +1370,11 @@ EXPORT_SYMBOL(remove_arg_zero);
  */
 int search_binary_handler(struct linux_binprm *bprm)
 {
-	unsigned int depth = bprm->recursion_depth;
-	int try,retval;
+	int try, retval;
 	struct linux_binfmt *fmt;
 
 	/* This allows 4 levels of binfmt rewrites before failing hard. */
-	if (depth > 5)
+	if (bprm->recursion_depth > 5)
 		return -ELOOP;
 
 	retval = security_bprm_check(bprm);
@@ -1396,9 +1395,9 @@ int search_binary_handler(struct linux_binprm *bprm)
 			if (!try_module_get(fmt->module))
 				continue;
 			read_unlock(&binfmt_lock);
-			bprm->recursion_depth = depth + 1;
+			bprm->recursion_depth++;
 			retval = fn(bprm);
-			bprm->recursion_depth = depth;
+			bprm->recursion_depth--;
 			if (retval >= 0) {
 				put_binfmt(fmt);
 				allow_write_access(bprm->file);