From: ChenXiaoSong <chenxiaosong2@huawei.com>
Date: Wed, 27 Jul 2022 17:21:52 -0700
Subject: xfs: fix NULL pointer dereference in xfs_getbmap()
Git-commit: 001c179c4e26d04db8c9f5e3fef9558b58356be6
Patch-mainline: v5.20-rc1
References: git-fixes
Reproducer:
1. fallocate -l 100M image
2. mkfs.xfs -f image
3. mount image /mnt
4. setxattr("/mnt", "trusted.overlay.upper", NULL, 0, XATTR_CREATE)
5. char arg[32] = "\x01\xff\x00\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x08\x00\x00\x00\xc6\x2a\xf7";
fd = open("/mnt", O_RDONLY|O_DIRECTORY);
ioctl(fd, _IOC(_IOC_READ|_IOC_WRITE, 0x58, 0x2c, 0x20), arg);
NULL pointer dereference will occur when race happens between xfs_getbmap()
and xfs_bmap_set_attrforkoff():
ioctl | setxattr
----------------------------|---------------------------
xfs_getbmap |
xfs_ifork_ptr |
xfs_inode_has_attr_fork |
ip->i_forkoff == 0 |
return NULL |
ifp == NULL |
| xfs_bmap_set_attrforkoff
| ip->i_forkoff > 0
xfs_inode_has_attr_fork |
ip->i_forkoff > 0 |
ifp == NULL |
ifp->if_format |
Fix this by locking i_lock before xfs_ifork_ptr().
Fixes: abbf9e8a4507 ("xfs: rewrite getbmap using the xfs_iext_* helpers")
Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Signed-off-by: Guo Xuenan <guoxuenan@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: added fixes tag]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Acked-by: Nikolay Borisov <nborisov@suse.com>
---
fs/xfs/xfs_bmap_util.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -533,29 +533,27 @@ xfs_getbmap(
whichfork = XFS_COW_FORK;
else
whichfork = XFS_DATA_FORK;
- ifp = XFS_IFORK_PTR(ip, whichfork);
xfs_ilock(ip, XFS_IOLOCK_SHARED);
switch (whichfork) {
case XFS_ATTR_FORK:
+ lock = xfs_ilock_attr_map_shared(ip);
if (!XFS_IFORK_Q(ip))
- goto out_unlock_iolock;
+ goto out_unlock_ilock;
max_len = 1LL << 32;
- lock = xfs_ilock_attr_map_shared(ip);
break;
case XFS_COW_FORK:
+ lock = XFS_ILOCK_SHARED;
+ xfs_ilock(ip, lock);
/* No CoW fork? Just return */
- if (!ifp)
+ if (!XFS_IFORK_PTR(ip, whichfork))
goto out_unlock_iolock;
if (xfs_get_cowextsz_hint(ip))
max_len = mp->m_super->s_maxbytes;
else
max_len = XFS_ISIZE(ip);
-
- lock = XFS_ILOCK_SHARED;
- xfs_ilock(ip, lock);
break;
case XFS_DATA_FORK:
if (!(iflags & BMV_IF_DELALLOC) &&
@@ -585,6 +583,8 @@ xfs_getbmap(
break;
}
+ ifp = XFS_IFORK_PTR(ip, whichfork);
+
switch (XFS_IFORK_FORMAT(ip, whichfork)) {
case XFS_DINODE_FMT_EXTENTS:
case XFS_DINODE_FMT_BTREE: