[PATCH 2/7] exec: Make unlocking exec_update_mutex explict

[Eric W. Biederman]

With install_exec_creds updated to follow immediately after
setup_new_exec, the failure of unshare_sighand is the only
code path where exec_update_mutex is held but not explicitly
unlocked.

Update that code path to explicitly unlock exec_update_mutex.

Remove the unlocking of exec_update_mutex from free_bprm.

Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com>
---
 fs/exec.c               | 6 +++---
 include/linux/binfmts.h | 3 +--
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 06b4c550af5d..6bd82a007bfc 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1344,7 +1344,7 @@ int flush_old_exec(struct linux_binprm * bprm)
         */
        retval = unshare_sighand(me);
        if (retval)
-               goto out;
+               goto out_unlock;
 
        set_fs(USER_DS);
        me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
@@ -1361,6 +1361,8 @@ int flush_old_exec(struct linux_binprm * bprm)
        do_close_on_exec(me->files);
        return 0;
 
+out_unlock:
+       mutex_unlock(&me->signal->exec_update_mutex);
 out:
        return retval;
 }
@@ -1477,8 +1479,6 @@ static void free_bprm(struct linux_binprm *bprm)
 {
        free_arg_pages(bprm);
        if (bprm->cred) {
-               if (bprm->called_exec_mmap)
-                       mutex_unlock(&current->signal->exec_update_mutex);
                mutex_unlock(&current->signal->cred_guard_mutex);
                abort_creds(bprm->cred);
        }
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index a345d9fed3d8..6f564b9ad882 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -47,8 +47,7 @@ struct linux_binprm {
                secureexec:1,
                /*
                 * Set by flush_old_exec, when exec_mmap has been called.
-                * This is past the point of no return, when the
-                * exec_update_mutex has been taken.
+                * This is past the point of no return.
                 */
                called_exec_mmap:1;
 #ifdef __alpha__
-- 
2.20.1