From: Jens Axboe <axboe@kernel.dk>
To: Cengiz Can <cengiz@kernel.wtf>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] blktrace: fix dereference after null check
Date: Thu, 5 Mar 2020 13:43:04 -0700 [thread overview]
Message-ID: <e6fe9883-2f51-a249-c5d2-ce11f6b449da@kernel.dk> (raw)
In-Reply-To: <20200304105818.11781-1-cengiz@kernel.wtf>
On 3/4/20 3:58 AM, Cengiz Can wrote:
> There was a recent change in blktrace.c that added a RCU protection to
> `q->blk_trace` in order to fix a use-after-free issue during access.
>
> However the change missed an edge case that can lead to dereferencing of
> `bt` pointer even when it's NULL:
>
> Coverity static analyzer marked this as a FORWARD_NULL issue with CID
> 1460458.
>
> ```
> /kernel/trace/blktrace.c: 1904 in sysfs_blk_trace_attr_store()
> 1898 ret = 0;
> 1899 if (bt == NULL)
> 1900 ret = blk_trace_setup_queue(q, bdev);
> 1901
> 1902 if (ret == 0) {
> 1903 if (attr == &dev_attr_act_mask)
>>>> CID 1460458: Null pointer dereferences (FORWARD_NULL)
>>>> Dereferencing null pointer "bt".
> 1904 bt->act_mask = value;
> 1905 else if (attr == &dev_attr_pid)
> 1906 bt->pid = value;
> 1907 else if (attr == &dev_attr_start_lba)
> 1908 bt->start_lba = value;
> 1909 else if (attr == &dev_attr_end_lba)
> ```
>
> Added a reassignment with RCU annotation to fix the issue.
Applied, thanks.
--
Jens Axboe
prev parent reply other threads:[~2020-03-05 20:43 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 10:58 [PATCH v2] blktrace: fix dereference after null check Cengiz Can
2020-03-05 8:47 ` Ming Lei
2020-03-05 10:13 ` Bob Liu
2020-03-05 14:05 ` Steven Rostedt
2020-03-05 20:43 ` Jens Axboe [this message]
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=e6fe9883-2f51-a249-c5d2-ce11f6b449da@kernel.dk \
--to=axboe@kernel.dk \
--cc=cengiz@kernel.wtf \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=rostedt@goodmis.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).