f2fs: fix use-after-free issue

During umount, f2fs_put_super() unregisters procfs entries after
f2fs_destroy_segment_manager(), it may cause use-after-free
issue when umount races with procfs accessing, fix it by relocating
f2fs_unregister_sysfs().

[Chao Yu: change commit title/message a bit]

Signed-off-by: Li Guifu <bluce.liguifu@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 80cb7cd358f8498150934b183ed327417b0d82f1..5e0a3eeb8ca465f0f666ca4c69617d039f2c6e94 100644 (file)
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1175,6 +1175,9 @@ static void f2fs_put_super(struct super_block *sb)
        int i;
        bool dropped;
 
+       /* unregister procfs/sysfs entries in advance to avoid race case */
+       f2fs_unregister_sysfs(sbi);
+
        f2fs_quota_off_umount(sb);
 
        /* prevent remaining shrinker jobs */
@@ -1240,8 +1243,6 @@ static void f2fs_put_super(struct super_block *sb)
 
        kvfree(sbi->ckpt);
 
-       f2fs_unregister_sysfs(sbi);
-
        sb->s_fs_info = NULL;
        if (sbi->s_chksum_driver)
                crypto_free_shash(sbi->s_chksum_driver);