[PATCH 2/3] exec: Make unlocking exec_update_mutex explict

Eric W. Biederman
2020-04-07T01:34:43Z

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" <ebiederm@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 d55710a36056..28c87020da9b 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1318,7 +1318,7 @@ 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 |
@@ -1335,6 +1335,8 @@ 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;
}
@@ -1451,8 +1453,6 @@ 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__
--
2.25.0