From 1bb933fb1fa8e4cb337a0d5dfd2ff4c0dc2073e8 Mon Sep 17 00:00:00 2001 From: Lukas Czerner Date: Fri, 20 May 2011 13:55:29 -0400 Subject: [PATCH] ext4: fix possible use-after-free in ext4_remove_li_request() We need to take reference to the s_li_request after we take a mutex, because it might be freed since then, hence result in accessing old already freed memory. Also we should protect the whole ext4_remove_li_request() because ext4_li_info might be in the process of being freed in ext4_lazyinit_thread(). Signed-off-by: Lukas Czerner Signed-off-by: "Theodore Ts'o" Reviewed-by: Eric Sandeen --- fs/ext4/super.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index fd51a4a266b6..ed5e80ef48c4 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2735,14 +2735,16 @@ static void ext4_remove_li_request(struct ext4_li_request *elr) static void ext4_unregister_li_request(struct super_block *sb) { - struct ext4_li_request *elr = EXT4_SB(sb)->s_li_request; - - if (!ext4_li_info) + mutex_lock(&ext4_li_mtx); + if (!ext4_li_info) { + mutex_unlock(&ext4_li_mtx); return; + } mutex_lock(&ext4_li_info->li_list_mtx); - ext4_remove_li_request(elr); + ext4_remove_li_request(EXT4_SB(sb)->s_li_request); mutex_unlock(&ext4_li_info->li_list_mtx); + mutex_unlock(&ext4_li_mtx); } static struct task_struct *ext4_lazyinit_task; -- 2.20.1