4.19-stable review patch. If anyone has any objections, please let me know.
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From: Fedor Pchelkin pchelkin@ispras.ru
[ 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).
Fixes: 04dc715e24d0 ("apparmor: audit policy ns specified in policy load") 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 --- 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 41da5ccc3f3e..683f551ec33b 100644 --- a/security/apparmor/policy_unpack.c +++ b/security/apparmor/policy_unpack.c @@ -635,6 +635,10 @@ 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";