From: David Howells <dhowells@redhat.com>
To: torvalds@linux-foundation.org
Cc: Sachin Sant <sachinp@linux.vnet.ibm.com>,
Hillf Danton <hdanton@sina.com>,
Sachin Sant <sachinp@linux.vnet.ibm.com>,
dhowells@redhat.com, keyrings@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH] keys: Fix missing null pointer check in request_key_auth_describe()
Date: Mon, 02 Sep 2019 13:37:29 +0100 [thread overview]
Message-ID: <156742784963.20310.17991758398365196262.stgit@warthog.procyon.org.uk> (raw)
From: Hillf Danton <hdanton@sina.com>
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>
---
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 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;
reply other threads:[~2019-09-02 12:37 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=156742784963.20310.17991758398365196262.stgit@warthog.procyon.org.uk \
--to=dhowells@redhat.com \
--cc=hdanton@sina.com \
--cc=keyrings@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=sachinp@linux.vnet.ibm.com \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).