From: Dave Jones <davej@redhat.com>
To: Linux Kernel <linux-kernel@vger.kernel.org>,
Al Viro <viro@ZenIV.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Subject: Re: 3.6-rc4 audit_log_d_path oops.
Date: Thu, 6 Sep 2012 11:16:16 -0400 [thread overview]
Message-ID: <20120906151616.GB23345@redhat.com> (raw)
In-Reply-To: <20120906134628.GA8962@redhat.com>
On Thu, Sep 06, 2012 at 09:46:28AM -0400, Dave Jones wrote:
> Hit this in overnight fuzz testing..
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
> IP: [<ffffffff81103365>] audit_log_d_path+0x35/0xf0
> PGD 12fded067 PUD 142c06067 PMD 0
> Oops: 0000 [#1] SMP
> Modules linked in: tun fuse ipt_ULOG binfmt_misc nfnetlink nfc caif_socket caif phonet can llc2 pppoe pppox ppp_generic slhc irda crc_ccitt rds af_key decnet rose x25 atm netrom appletalk ipx p8023 psnap p8022 llc ax25 lockd sunrpc bluetooth rfkill ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack kvm_intel kvm crc32c_intel ghash_clmulni_intel microcode pcspkr i2c_i801 e1000e uinput i915 video i2c_algo_bit drm_kms_helper drm i2c_core
> CPU 5
> Pid: 7007, comm: trinity-child5 Not tainted 3.6.0-rc4+ #36
> RIP: 0010:[<ffffffff81103365>] [<ffffffff81103365>] audit_log_d_path+0x35/0xf0
> RSP: 0018:ffff880116b33ec8 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000035
> RDX: ffffffff819dbf5d RSI: ffffffff819da5bb RDI: 0000000000000000
> RBP: ffff880116b33ee8 R08: ffff88001942533e R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000000 R12: ffff880116b33f38
> R13: ffff880116b33f38 R14: ffffffff819fa1eb R15: 0000000000000005
> FS: 00007f5742581740(0000) GS:ffff880148600000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000020 CR3: 00000001046d3000 CR4: 00000000001407e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process trinity-child5 (pid: 7007, threadinfo ffff880116b32000, task ffff880019424d00)
> Stack:
> ffff880116b33ee8 0000000000000000 ffff880116b33f38 ffff880019424d00
> ffff880116b33f18 ffffffff81103522 00000000000001d0 ffff880119ed6500
> 00000000000001d0 0000000000000109 ffff880116b33f78 ffffffff811ebb95
> Call Trace:
> [<ffffffff81103522>] audit_log_link_denied+0x92/0x100
> [<ffffffff811ebb95>] sys_linkat+0x195/0x1e0
> [<ffffffff813573de>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> [<ffffffff816a50ed>] system_call_fastpath+0x1a/0x1f
> Code: 5d e8 4c 89 65 f0 4c 89 6d f8 0f 1f 44 00 00 48 85 f6 48 89 fb 49 89 d5 74 11 48 89 f2 31 c0 48 c7 c6 bb a5 9d 81 e8 8b e1 ff ff <8b> 73 20 40 f6 c6 01 75 62 48 8b 3d 33 33 93 01 48 85 ff 74 4e
> RIP [<ffffffff81103365>] audit_log_d_path+0x35/0xf0
> RSP <ffff880116b33ec8>
> CR2: 0000000000000020
> ---[ end trace 85b88c850143bb1c ]---
>
> That's here in kernel/audit.c
>
> 1433
> 1434 /* We will allow 11 spaces for ' (deleted)' to be appended */
> 1435 pathname = kmalloc(PATH_MAX+11, ab->gfp_mask);
>
> 'ab' is NULL.
>
> Looks like audit_log_link_denied needs to handle potential failure from
> audit_log_start and abort early. (oddly, it looks like every other
> function called there checks for !ab.)
>
> Maybe additional code should be added here to printk the audit message
> to dmesg so that we don't lose it entirely, but for now, minimal fix.
>
> Signed-off-by: Dave Jones <davej@redhat.com>
>
> diff --git a/kernel/audit.c b/kernel/audit.c
> index ea3b7b6..c3e85bb 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -1466,6 +1466,9 @@ void audit_log_link_denied(const char *operation, struct path *link)
>
> ab = audit_log_start(current->audit_context, GFP_KERNEL,
> AUDIT_ANOM_LINK);
> + if (!ab)
> + return;
> +
> audit_log_format(ab, "op=%s action=denied", operation);
> audit_log_format(ab, " pid=%d comm=", current->pid);
> audit_log_untrustedstring(ab, current->comm);
Added Kees, as this was introduced in a51d9eaa41866ab6b4b6ecad7b621f8b66ece0dc
I just realised, the funny thing about this is that the machine running that test
had selinux/audit disabled. And yet here we are, screwing around with audit buffers.
Should there be a test on audit_enable=0 in audit_log_link_denied() ?
I'm now curious how much more of the audit code is getting run through similar lack of tests
Dave
next prev parent reply other threads:[~2012-09-06 15:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-06 13:46 3.6-rc4 audit_log_d_path oops Dave Jones
2012-09-06 15:08 ` Check all returns from audit_log_start Dave Jones
2012-09-06 15:36 ` Eric Paris
2012-09-06 15:47 ` Dave Jones
2012-09-06 15:56 ` Dave Jones
2012-09-06 15:16 ` Dave Jones [this message]
2012-09-06 15:34 ` 3.6-rc4 audit_log_d_path oops Eric Paris
2012-09-06 16:32 ` Kees Cook
2012-09-06 16:45 ` Dave Jones
2012-09-06 17:50 ` Kees Cook
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=20120906151616.GB23345@redhat.com \
--to=davej@redhat.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=viro@ZenIV.linux.org.uk \
/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).