[PATCH v2] fs/squashfs: restrict length of xattr_ids in read_xattr_id_table

From: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
To: lkp@intel.com
Cc: clang-built-linux@googlegroups.com, kbuild-all@lists.01.org,
	linux-kernel@vger.kernel.org, phillip@squashfs.org.uk,
	snovitoll@gmail.com,
	syzbot+2ccea6339d368360800d@syzkaller.appspotmail.com
Subject: [PATCH v2] fs/squashfs: restrict length of xattr_ids in read_xattr_id_table
Date: Wed,  3 Feb 2021 19:45:16 +0600	[thread overview]
Message-ID: <20210203134516.1697931-1-snovitoll@gmail.com> (raw)
In-Reply-To: <202102032044.wrsk1CfP-lkp@intel.com>

In PATCH v2 fixed return -ENOMEM as error pointer.

>syzbot found WARNING in squashfs_read_table [1] when length of xattr_ids
>exceeds KMALLOC_MAX_SIZE in squashfs_read_table() for kmalloc().
>
>For other squashfs tables, currently such as boundary is checked with
>another table's boundaries. Xattr table is the last one, so there is
>no defined limit. But to avoid order >= MAX_ORDER warning condition,
>we should restrict SQUASHFS_XATTR_BLOCK_BYTES(*xattr_ids) to
>KMALLOC_MAX_SIZE, and it gives 1024 pages in squashfs_read_table via
>(length + PAGE_SIZE - 1) >> PAGE_SHIFT.
>
>[1]
>Call Trace:
> alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
> alloc_pages include/linux/gfp.h:547 [inline]
> kmalloc_order+0x2e/0xb0 mm/slab_common.c:916
> kmalloc_order_trace+0x14/0x120 mm/slab_common.c:932
> kmalloc include/linux/slab.h:559 [inline]
> squashfs_read_table+0x43/0x1e0 fs/squashfs/cache.c:413
> squashfs_read_xattr_id_table+0x191/0x220 fs/squashfs/xattr_id.c:81

Reported-by: syzbot+2ccea6339d368360800d@syzkaller.appspotmail.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
---
 fs/squashfs/xattr_id.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/squashfs/xattr_id.c b/fs/squashfs/xattr_id.c
index d99e08464554..2462876c66c4 100644
--- a/fs/squashfs/xattr_id.c
+++ b/fs/squashfs/xattr_id.c
@@ -78,5 +78,8 @@ __le64 *squashfs_read_xattr_id_table(struct super_block *sb, u64 start,
 
 	TRACE("In read_xattr_index_table, length %d\n", len);
 
+	if (len > KMALLOC_MAX_SIZE)
+		return ERR_PTR(-ENOMEM);
+
 	return squashfs_read_table(sb, start + sizeof(*id_table), len);
 }
-- 
2.25.1

