linux-kernel - [PATCH v6 01/15] ubifs: rename_whiteout: Fix double free for whiteout

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Message-ID: <20211227032246.2886878-2-chengzhihao1@huawei.com>
Date:   Mon, 27 Dec 2021 11:22:32 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     <richard@....at>, <miquel.raynal@...tlin.com>, <vigneshr@...com>,
        <mcoquelin.stm32@...il.com>, <kirill.shutemov@...ux.intel.com>,
        <s.hauer@...gutronix.de>
CC:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v6 01/15] ubifs: rename_whiteout: Fix double free for whiteout_ui->data

'whiteout_ui->data' will be freed twice if space budget fail for
rename whiteout operation as following process:

rename_whiteout
  dev = kmalloc
  whiteout_ui->data = dev
  kfree(whiteout_ui->data)  // Free first time
  iput(whiteout)
    ubifs_free_inode
      kfree(ui->data)	    // Double free!

KASAN reports:
==================================================================
BUG: KASAN: double-free or invalid-free in ubifs_free_inode+0x4f/0x70
Call Trace:
  kfree+0x117/0x490
  ubifs_free_inode+0x4f/0x70 [ubifs]
  i_callback+0x30/0x60
  rcu_do_batch+0x366/0xac0
  __do_softirq+0x133/0x57f

Allocated by task 1506:
  kmem_cache_alloc_trace+0x3c2/0x7a0
  do_rename+0x9b7/0x1150 [ubifs]
  ubifs_rename+0x106/0x1f0 [ubifs]
  do_syscall_64+0x35/0x80

Freed by task 1506:
  kfree+0x117/0x490
  do_rename.cold+0x53/0x8a [ubifs]
  ubifs_rename+0x106/0x1f0 [ubifs]
  do_syscall_64+0x35/0x80

The buggy address belongs to the object at ffff88810238bed8 which
belongs to the cache kmalloc-8 of size 8
==================================================================

Let ubifs_free_inode() free 'whiteout_ui->data'. BTW, delete unused
assignment 'whiteout_ui->data_len = 0', process 'ubifs_evict_inode()
-> ubifs_jnl_delete_inode() -> ubifs_jnl_write_inode()' doesn't need it
(because 'inc_nlink(whiteout)' won't be excuted by 'goto out_release',
 and the nlink of whiteout inode is 0).

Fixes: 9e0a1fff8db56ea ("ubifs: Implement RENAME_WHITEOUT")
Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
---
 fs/ubifs/dir.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 7c61d0ec0159..cfa8881d8cca 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -1425,8 +1425,6 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry,
 
 		err = ubifs_budget_space(c, &wht_req);
 		if (err) {
-			kfree(whiteout_ui->data);
-			whiteout_ui->data_len = 0;
 			iput(whiteout);
 			goto out_release;
 		}
-- 
2.31.1