linux-kernel - [PATCH 2/3] exec: Make unlocking exec_update

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87imic3wtz.fsf_-_@x220.int.ebiederm.org>
Date:   Mon, 06 Apr 2020 20:31:52 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Bernd Edlinger <bernd.edlinger@...mail.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexey Gladkov <gladkov.alexey@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: [PATCH 2/3] exec: Make unlocking exec_update_mutex explict


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@...ssion.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