From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Hillf Danton <hdanton@sina.com>,
Sachin Sant <sachinp@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Sasha Levin <sashal@kernel.org>,
keyrings@vger.kernel.org, linux-security-module@vger.kernel.org
Subject: [PATCH AUTOSEL 4.19 6/8] keys: Fix missing null pointer check in request_key_auth_describe()
Date: Mon, 9 Sep 2019 11:41:21 -0400 [thread overview]
Message-ID: <20190909154124.31146-6-sashal@kernel.org> (raw)
In-Reply-To: <20190909154124.31146-1-sashal@kernel.org>
From: Hillf Danton <hdanton@sina.com>
[ Upstream commit d41a3effbb53b1bcea41e328d16a4d046a508381 ]
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.
[DH: Modified to not take already-held rcu lock and modified to also check
in the read routine]
Fixes: 04c567d9313e ("[PATCH] Keys: Fix race between two instantiators of a key")
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Hillf Danton <hdanton@sina.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
security/keys/request_key_auth.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index 5e515791ccd11..1d34b2a5f485e 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -71,6 +71,9 @@ static void request_key_auth_describe(const struct key *key,
{
struct request_key_auth *rka = get_request_key_auth(key);
+ if (!rka)
+ return;
+
seq_puts(m, "key:");
seq_puts(m, key->description);
if (key_is_positive(key))
@@ -88,6 +91,9 @@ 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;
--
2.20.1
parent reply other threads:[~2019-09-09 22:16 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <20190909154124.31146-1-sashal@kernel.org>]
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