xfs: fix NULL pointer dereference in xfs_getbmap()
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>
1 file changed
