unfuck binfmt_misc.c (broken by commit e6084d4)

scanarg(s, del) never returns s; the empty field results in s + 1.
Restore the correct checks, and move NUL-termination into scanarg(),
while we are at it.

Incidentally, mixing "coding style cleanups" (for small values of cleanup)
with functional changes is a Bad Idea(tm)...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 3 insertions, 4 deletions

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index c04ef1d4f18a..97aff2879cda 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -254,6 +254,7 @@ static char *scanarg(char *s, char del)
                                 return NULL;
                 }
         }
+        s[-1] ='\0';
         return s;
 }
 
@@ -378,8 +379,7 @@ static Node *create_entry(const char __user *buffer, size_t count)
                 p = scanarg(p, del);
                 if (!p)
                         goto einval;
-                p[-1] = '\0';
-                if (p == e->magic)
+                if (!e->magic[0])
                         goto einval;
                 if (USE_DEBUG)
                         print_hex_dump_bytes(
@@ -391,8 +391,7 @@ static Node *create_entry(const char __user *buffer, size_t count)
                 p = scanarg(p, del);
                 if (!p)
                         goto einval;
-                p[-1] = '\0';
-                if (p == e->mask) {
+                if (!e->mask[0]) {
                         e->mask = NULL;
                         pr_debug("register:  mask[raw]: none\n");
                 } else if (USE_DEBUG)