| Date | Wed, 01 Jun 2011 16:59:29 +0900 | From | Greg KH <> | Subject | [033/146] ext4: fix possible use-after-free in |
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2.6.38-stable review patch. If anyone has any objections, please let us know.
------------------ ext4_remove_li_request()
From: Lukas Czerner <lczerner@redhat.com>
commit 1bb933fb1fa8e4cb337a0d5dfd2ff4c0dc2073e8 upstream.
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 <lczerner@redhat.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Reviewed-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/ext4/super.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2716,14 +2716,16 @@ static void ext4_remove_li_request(struc 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;
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