On 12/28/23 08:07, Fedor Pchelkin wrote:
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).
Fixes: 04dc715e24d0 ("apparmor: audit policy ns specified in policy load")
Signed-off-by: Fedor Pchelkin <[email protected]>
thanks, I have pulled this into my tree
Acked-by: John Johansen <[email protected]>
---
security/apparmor/policy_unpack.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/security/apparmor/policy_unpack.c
b/security/apparmor/policy_unpack.c
index e0af1e9f40ee..70d448048773 100644
--- a/security/apparmor/policy_unpack.c
+++ b/security/apparmor/policy_unpack.c
@@ -835,6 +835,10 @@ static struct aa_profile *unpack_profile(struct aa_ext *e,
char **ns_name)
tmpname = aa_splitn_fqname(name, strlen(name), &tmpns, &ns_len);
if (tmpns) {
+ if (!tmpname) {
+ info = "empty profile name";
+ goto fail;
+ }
*ns_name = kstrndup(tmpns, ns_len, GFP_KERNEL);
if (!*ns_name) {
info = "out of memory";
