[PATCH AUTOSEL 4.20 270/304] f2fs: fix use-after-free issue when accessing sbi->stat_info

Sasha Levin
2019-01-28T15:57:26Z

From: Sahitya Tummala <stummala@codeaurora.org>

[ Upstream commit 60aa4d5536ab7fe32433ca1173bd9d6633851f27 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/super.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 855a622fb052..a239472f405a 100644
--- 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:
--
2.19.1