tree 88c8de8922ea239433c234967c58168a550015b7
parent 1f94d5205d2ad9350878e947097be6ae88f45aa4
author Fedor Pchelkin <pchelkin@ispras.ru> 1703779663 +0300
committer He Gao <hegao@google.com> 1710873348 +0000

apparmor: avoid crash when parsed profile name is empty

[ Upstream commit 55a8210c9e7d21ff2644809699765796d4bfb200 ]

When processing a packed profile in unpack_profile() described like

 "profile :ns::samba-dcerpcd /usr/lib*/samba/{,samba/}samba-dcerpcd {...}"

a string ":samba-dcerpcd" is unpacked as a fully-qualified name and then
passed to aa_splitn_fqname().

aa_splitn_fqname() treats ":samba-dcerpcd" as only containing a namespace.
Thus it returns NULL for tmpname, meanwhile tmpns is non-NULL. Later
aa_alloc_profile() crashes as the new profile name is NULL now.

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 6 PID: 1657 Comm: apparmor_parser Not tainted 6.7.0-rc2-dirty #16
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014
RIP: 0010:strlen+0x1e/0xa0
Call Trace:
 <TASK>
 ? strlen+0x1e/0xa0
 aa_policy_init+0x1bb/0x230
 aa_alloc_profile+0xb1/0x480
 unpack_profile+0x3bc/0x4960
 aa_unpack+0x309/0x15e0
 aa_replace_profiles+0x213/0x33c0
 policy_update+0x261/0x370
 profile_replace+0x20e/0x2a0
 vfs_write+0x2af/0xe00
 ksys_write+0x126/0x250
 do_syscall_64+0x46/0xf0
 entry_SYSCALL_64_after_hwframe+0x6e/0x76
 </TASK>
---[ end trace 0000000000000000 ]---
RIP: 0010:strlen+0x1e/0xa0

It seems such behaviour of aa_splitn_fqname() is expected and checked in
other places where it is called (e.g. aa_remove_profiles). Well, there
is an explicit comment "a ns name without a following profile is allowed"
inside.

AFAICS, nothing can prevent unpacked "name" to be in form like
":samba-dcerpcd" - it is passed from userspace.

Deny the whole profile set replacement in such case and inform user with
EPROTO and an explaining message.

Found by Linux Verification Center (linuxtesting.org).

BUG=b/329820389
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2023-52443 in the Linux kernel.

Fixes: 04dc715e24d0 ("apparmor: audit policy ns specified in policy load")
Change-Id: I64da66f4db1a077abe7557bc4591c7b47b65ae6c
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/67153
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Michael Kochera <kochera@google.com>