binfmt_misc: use credential guards

Use credential guards for scoped credential override with automatic
restoration on scope exit.

Link: https://patch.msgid.link/20251103-work-creds-guards-simple-v1-8-a3e156839e7f@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index a839f960cd4a00323bf34f733ca0faa4cbca9b8e..558db4bd6c2abc4313f4292574110addbde777e9 100644 (file)
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -782,8 +782,6 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
                return PTR_ERR(e);
 
        if (e->flags & MISC_FMT_OPEN_FILE) {
-               const struct cred *old_cred;
-
                /*
                 * Now that we support unprivileged binfmt_misc mounts make
                 * sure we use the credentials that the register @file was
@@ -791,9 +789,8 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
                 * didn't matter much as only a privileged process could open
                 * the register file.
                 */
-               old_cred = override_creds(file->f_cred);
-               f = open_exec(e->interpreter);
-               revert_creds(old_cred);
+               scoped_with_creds(file->f_cred)
+                       f = open_exec(e->interpreter);
                if (IS_ERR(f)) {
                        pr_notice("register: failed to install interpreter file %s\n",
                                 e->interpreter);