proc: s_fs_info may be NULL when proc_kill_sb is called

syzbot found that proc_fill_super() fails before filling up sb->s_fs_info, deactivate_locked_super() will be called and sb->s_fs_info will be NULL. The proc_kill_sb() does not expect fs_info to be NULL which is wrong. Link: https://lore.kernel.org/lkml/0000000000002d7ca605a7b8b1c5@google.com Reported-by: syzbot+4abac52934a48af5ff19@syzkaller.appspotmail.com Fixes: fa10fed ("proc: allow to mount many instances of proc in one pid namespace") Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
bon3less · Jun 10, 2020 · 058f2e4 · 058f2e4
1 parent 9d78ede
commit 058f2e4
Showing 1 changed file with 6 additions and 4 deletions.
diff --git a/fs/proc/root.c b/fs/proc/root.c
@@ -264,11 +264,13 @@ static void proc_kill_sb(struct super_block *sb)
 {
 	struct proc_fs_info *fs_info = proc_sb_info(sb);
 
-	if (fs_info->proc_self)
-		dput(fs_info->proc_self);
+	if (!fs_info) {
+		kill_anon_super(sb);
+		return;
+	}
 
-	if (fs_info->proc_thread_self)
-		dput(fs_info->proc_thread_self);
+	dput(fs_info->proc_self);
+	dput(fs_info->proc_thread_self);
 
 	kill_anon_super(sb);
 	put_pid_ns(fs_info->pid_ns);