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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 5.2 10/12] keys: Fix missing null pointer check in request_key_auth_describe()
Date: Mon,  9 Sep 2019 11:40:50 -0400	[thread overview]
Message-ID: <20190909154052.30941-10-sashal@kernel.org> (raw)
In-Reply-To: <20190909154052.30941-1-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 e45b5cf3b97fd..8491becb57270 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 = get_request_key_auth(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;
 
-- 
2.20.1


  parent reply	other threads:[~2019-09-09 22:18 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09 15:40 [PATCH AUTOSEL 5.2 01/12] arm64: dts: renesas: r8a77995: draak: Fix backlight regulator name Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 02/12] dmaengine: ti: dma-crossbar: Fix a memory leak bug Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 03/12] dmaengine: ti: omap-dma: Add cleanup in omap_dma_probe() Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 04/12] x86/uaccess: Don't leak the AC flags into __get_user() argument evaluation Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 05/12] x86/hyper-v: Fix overflow bug in fill_gva_list() Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 06/12] configfs_register_group() shouldn't be (and isn't) called in rmdirable parts Sasha Levin
2019-09-10  6:01   ` Christoph Hellwig
2019-09-10  9:19     ` Greg KH
2019-09-10 10:46       ` Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 07/12] iommu/vt-d: Remove global page flush support Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 08/12] dmaengine: sprd: Fix the DMA link-list configuration Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 09/12] dmaengine: rcar-dmac: Fix DMACHCLR handling if iommu is mapped Sasha Levin
2019-09-09 15:40 ` Sasha Levin [this message]
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 11/12] iommu/amd: Flush old domains in kdump kernel Sasha Levin
2019-09-09 15:40 ` [PATCH AUTOSEL 5.2 12/12] iommu/amd: Fix race in increase_address_space() Sasha Levin

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