f2fs: fix use-after-free issue when accessing sbi->stat_info

iput() on sbi->node_inode can update sbi->stat_info
in the below context, if the f2fs_write_checkpoint()
has failed with error.

f2fs_balance_fs_bg+0x1ac/0x1ec
f2fs_write_node_pages+0x4c/0x260
do_writepages+0x80/0xbc
__writeback_single_inode+0xdc/0x4ac
writeback_single_inode+0x9c/0x144
write_inode_now+0xc4/0xec
iput+0x194/0x22c
f2fs_put_super+0x11c/0x1e8
generic_shutdown_super+0x70/0xf4
kill_block_super+0x2c/0x5c
kill_f2fs_super+0x44/0x50
deactivate_locked_super+0x60/0x8c
deactivate_super+0x68/0x74
cleanup_mnt+0x40/0x78

Fix this by moving f2fs_destroy_stats() further below iput() in
both f2fs_put_super() and f2fs_fill_super() paths.

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
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 9b17e367aa8c52d801912b8d011a10d357f4100c..c46a1d4318d419181713a44c11b917282352804b 100644 (file)
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1058,9 +1058,6 @@ static void f2fs_put_super(struct super_block *sb)
                f2fs_write_checkpoint(sbi, &cpc);
        }
 
-       /* f2fs_write_checkpoint can update stat informaion */
-       f2fs_destroy_stats(sbi);
-
        /*
         * normally superblock is clean, so we need to release this.
         * In addition, EIO will skip do checkpoint, we need this as well.
@@ -1080,6 +1077,12 @@ static void f2fs_put_super(struct super_block *sb)
        iput(sbi->node_inode);
        iput(sbi->meta_inode);
 
+       /*
+        * iput() can update stat information, if f2fs_write_checkpoint()
+        * above failed with error.
+        */
+       f2fs_destroy_stats(sbi);
+
        /* destroy f2fs internal modules */
        f2fs_destroy_node_manager(sbi);
        f2fs_destroy_segment_manager(sbi);
@@ -3256,30 +3259,30 @@ try_onemore:
 
        f2fs_build_gc_manager(sbi);
 
+       err = f2fs_build_stats(sbi);
+       if (err)
+               goto free_nm;
+
        /* get an inode for node space */
        sbi->node_inode = f2fs_iget(sb, F2FS_NODE_INO(sbi));
        if (IS_ERR(sbi->node_inode)) {
                f2fs_msg(sb, KERN_ERR, "Failed to read node inode");
                err = PTR_ERR(sbi->node_inode);
-               goto free_nm;
+               goto free_stats;
        }
 
-       err = f2fs_build_stats(sbi);
-       if (err)
-               goto free_node_inode;
-
        /* read root inode and dentry */
        root = f2fs_iget(sb, F2FS_ROOT_INO(sbi));
        if (IS_ERR(root)) {
                f2fs_msg(sb, KERN_ERR, "Failed to read root inode");
                err = PTR_ERR(root);
-               goto free_stats;
+               goto free_node_inode;
        }
        if (!S_ISDIR(root->i_mode) || !root->i_blocks ||
                        !root->i_size || !root->i_nlink) {
                iput(root);
                err = -EINVAL;
-               goto free_stats;
+               goto free_node_inode;
        }
 
        sb->s_root = d_make_root(root); /* allocate root dentry */
@@ -3403,12 +3406,12 @@ free_meta:
 free_root_inode:
        dput(sb->s_root);
        sb->s_root = NULL;
-free_stats:
-       f2fs_destroy_stats(sbi);
 free_node_inode:
        f2fs_release_ino_entry(sbi, true);
        truncate_inode_pages_final(NODE_MAPPING(sbi));
        iput(sbi->node_inode);
+free_stats:
+       f2fs_destroy_stats(sbi);
 free_nm:
        f2fs_destroy_node_manager(sbi);
 free_sm: