flat: fix uninitialized ptr with shared libs

The new credentials code broke load_flat_shared_library() as it now uses
an uninitialized cred pointer.

Reported-by: Bernd Schmidt <bernds_cb1@t-online.de>
Tested-by: Bernd Schmidt <bernds_cb1@t-online.de>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: David Howells <dhowells@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 5 deletions

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 697f6b5f1313..e92f229e3c6e 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -828,15 +828,22 @@ static int load_flat_shared_library(int id, struct lib_info *libs)
         if (IS_ERR(bprm.file))
                 return res;
 
+        bprm.cred = prepare_exec_creds();
+        res = -ENOMEM;
+        if (!bprm.cred)
+                goto out;
+
         res = prepare_binprm(&bprm);
 
         if (res <= (unsigned long)-4096)
                 res = load_flat_file(&bprm, libs, id, NULL);
-        if (bprm.file) {
-                allow_write_access(bprm.file);
-                fput(bprm.file);
-                bprm.file = NULL;
-        }
+
+        abort_creds(bprm.cred);
+
+out:
+        allow_write_access(bprm.file);
+        fput(bprm.file);
+
         return(res);
 }