From: David Howells <dhowells@redhat.com>
To: Sachin Sant <sachinp@linux.vnet.ibm.com>
Cc: dhowells@redhat.com, Hillf Danton <hdanton@sina.com>,
linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
keyrings@vger.kernel.org
Subject: Re: Oops (request_key_auth_describe) while running cve-2016-7042 from LTP
Date: Fri, 30 Aug 2019 16:13:34 +0100 [thread overview]
Message-ID: <11986.1567178014@warthog.procyon.org.uk> (raw)
In-Reply-To: <85B7196E-D717-4F19-A7E8-82A18287A3DE@linux.vnet.ibm.com>
Can you try this patch instead of Hillf's?
David
---
commit df882ad6d4e24a3763719c1798ea58e87d56c2d7
Author: Hillf Danton <hdanton@sina.com>
Date: Fri Aug 30 15:54:33 2019 +0100
keys: Fix missing null pointer check in request_key_auth_describe()
If a request_key authentication token key gets revoked, there's a window in
which request_key_auth_describe() can see it with a NULL payload - but it
makes no check for this and something like the following oops may occur:
BUG: Kernel NULL pointer dereference at 0x00000038
Faulting instruction address: 0xc0000000004ddf30
Oops: Kernel access of bad area, sig: 11 [#1]
...
NIP [...] request_key_auth_describe+0x90/0xd0
LR [...] request_key_auth_describe+0x54/0xd0
Call Trace:
[...] request_key_auth_describe+0x54/0xd0 (unreliable)
[...] proc_keys_show+0x308/0x4c0
[...] seq_read+0x3d0/0x540
[...] proc_reg_read+0x90/0x110
[...] __vfs_read+0x3c/0x70
[...] vfs_read+0xb4/0x1b0
[...] ksys_read+0x7c/0x130
[...] system_call+0x5c/0x70
Fix this by checking for a NULL pointer when describing such a key.
Also make the read routine check for a NULL pointer to be on the safe side.
Fixes: 04c567d9313e ("[PATCH] Keys: Fix race between two instantiators of a key")
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index e73ec040e250..ecba39c93fd9 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -66,6 +66,9 @@ static void request_key_auth_describe(const struct key *key,
{
struct request_key_auth *rka = dereference_key_rcu(key);
+ if (!rka)
+ return;
+
seq_puts(m, "key:");
seq_puts(m, key->description);
if (key_is_positive(key))
@@ -83,6 +86,9 @@ static long request_key_auth_read(const struct key *key,
size_t datalen;
long ret;
+ if (!rka)
+ return -EKEYREVOKED;
+
datalen = rka->callout_len;
ret = datalen;
next prev parent reply other threads:[~2019-08-30 15:13 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 6:48 Oops (request_key_auth_describe) while running cve-2016-7042 from LTP Sachin Sant
2019-08-30 15:13 ` David Howells [this message]
2019-08-31 4:57 ` Sachin Sant
2019-09-02 7:14 ` David Howells
[not found] <20190830145454.B91DF125411@zmta02.collab.prod.int.phx2.redhat.com>
[not found] ` <20190830085646.14740-1-hdanton@sina.com>
2019-08-30 10:32 ` Sachin Sant
2019-08-30 14:13 ` David Howells
2019-08-30 15:12 ` David Howells
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