[SRU][Xenial][PATCH 4/4] commoncap: Handle memory allocation failure.

[Seth Forshee]

From: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>

BugLink: http://bugs.launchpad.net/bugs/1778286

syzbot is reporting NULL pointer dereference at xattr_getsecurity() [1],
for cap_inode_getsecurity() is returning sizeof(struct vfs_cap_data) when
memory allocation failed. Return -ENOMEM if memory allocation failed.

[1] https://syzkaller.appspot.com/bug?id=a55ba438506fe68649a5f50d2d82d56b365e0107

Signed-off-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
Fixes: 8db6c34f1dbc8e06 ("Introduce v3 namespaced file capabilities")
Reported-by: syzbot <syzbot+9369930ca44f29e60e2d at syzkaller.appspotmail.com>
Cc: stable <stable at vger.kernel.org> # 4.14+
Acked-by: Serge E. Hallyn <serge at hallyn.com>
Acked-by: James Morris <james.morris at microsoft.com>
Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
(cherry picked from commit 1f5781725dcbb026438e77091c91a94f678c3522)
Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
---
 security/commoncap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/commoncap.c b/security/commoncap.c
index d42373adb762..814324f7f057 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -460,6 +460,8 @@ int cap_inode_getsecurity(const struct inode *inode, const char *name,
 				magic |= VFS_CAP_FLAGS_EFFECTIVE;
 			memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 			cap->magic_etc = cpu_to_le32(magic);
+		} else {
+			size = -ENOMEM;
 		}
 	}
 	kfree(tmpbuf);
-- 
2.17.0