[PATCH 4.9 27/39] xfs: Fix UBSAN null-ptr-deref in xfs_sysfs_init

Greg Kroah-Hartman
2020-08-24T09:27:21Z

From: Eiichi Tsukata <devel@etsukata.com>

[ Upstream commit 96cf2a2c75567ff56195fe3126d497a2e7e4379f ]

If xfs_sysfs_init is called with parent_kobj == NULL, UBSAN
shows the following warning:

UBSAN: null-ptr-deref in ./fs/xfs/xfs_sysfs.h:37:23
member access within null pointer of type 'struct xfs_kobj'
Call Trace:
dump_stack+0x10e/0x195
ubsan_type_mismatch_common+0x241/0x280
__ubsan_handle_type_mismatch_v1+0x32/0x40
init_xfs_fs+0x12b/0x28f
do_one_initcall+0xdd/0x1d0
do_initcall_level+0x151/0x1b6
do_initcalls+0x50/0x8f
do_basic_setup+0x29/0x2b
kernel_init_freeable+0x19f/0x20b
kernel_init+0x11/0x1e0
ret_from_fork+0x22/0x30

Fix it by checking parent_kobj before the code accesses its member.

Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
[darrick: minor whitespace edits]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/xfs/xfs_sysfs.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_sysfs.h b/fs/xfs/xfs_sysfs.h
index d04637181ef21..980c9429abec5 100644
--- a/fs/xfs/xfs_sysfs.h
+++ b/fs/xfs/xfs_sysfs.h
@@ -44,9 +44,11 @@ xfs_sysfs_init(
struct xfs_kobj *parent_kobj,
const char *name)
{
+ struct kobject *parent;
+
+ parent = parent_kobj ? &parent_kobj->kobject : NULL;
init_completion(&kobj->complete);
- return kobject_init_and_add(&kobj->kobject, ktype,
- &parent_kobj->kobject, "%s", name);
+ return kobject_init_and_add(&kobj->kobject, ktype, parent, "%s", name);
}

static inline void
--
2.25.1