linux-kernel - Re: [PATCH] blktrace: fix a bug in blk_msg

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 3 Apr 2009 14:52:50 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"Alan D. Brunelle" <alan.brunelle@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Carl Henrik Lunde <chlunde@...g.uio.no>
Subject: Re: [PATCH] blktrace: fix a bug in blk_msg_write()


* Jens Axboe <jens.axboe@...cle.com> wrote:

> On Fri, Apr 03 2009, Ingo Molnar wrote:
> > 
> > * Li Zefan <lizf@...fujitsu.com> wrote:
> > 
> > > This is another long-standing bug.
> > >
> > > ================
> > >
> > >
> > >  (console 1)
> > >  # echo -n 'a' > /sys/kernel/debug/block/sda/msg
> > >  (console 2)
> > >  # blktrace -d /dev/sda -a pc -o - | blkparse -i -
> > >   8,0    0        0     0.000000000     0  m   N a??????????????????@...???
> > >
> > > We should terminate the msg buffer with '\0'.
> > >
> > > Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> > > ---
> > >  kernel/trace/blktrace.c |    5 +++--
> > >  1 files changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> > > index c0ef70d..2bf341f 100644
> > > --- a/kernel/trace/blktrace.c
> > > +++ b/kernel/trace/blktrace.c
> > > @@ -327,10 +327,10 @@ static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
> > >  	char *msg;
> > >  	struct blk_trace *bt;
> > >
> > > -	if (count > BLK_TN_MAX_MSG)
> > > +	if (count >= BLK_TN_MAX_MSG)
> > >  		return -EINVAL;
> > >
> > > -	msg = kmalloc(count, GFP_KERNEL);
> > > +	msg = kmalloc(count + 1, GFP_KERNEL);
> > >  	if (msg == NULL)
> > >  		return -ENOMEM;
> > >
> > > @@ -338,6 +338,7 @@ static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
> > >  		kfree(msg);
> > >  		return -EFAULT;
> > >  	}
> > > +	msg[count] = '\0';
> > >
> > >  	bt = filp->private_data;
> > >  	__trace_note_message(bt, "%s", msg);
> > 
> > Nice fix!
> > 
> > Jens, do you ack this and should i add a Cc: <stable@...nel.org>
> > backporting tag?
> > 
> > This fix applies fine to v2.6.29 after:
> > 
> >    sed 's/kernel\/trace\/blktrace.c/block\/blktrace.c'
> 
> This is identical to the following patch from Carl Henrik Lunde, which
> he just ported to -tip. It has existed before, as a patch to 2.6.29-git,
> but was unfortunately dropped.
> 
> So is this a coincidence? If not, Carl Henrik Lunde should be credited.
> 
> >From f116bce73e04d01614fd28ea678e0953cc321155 Mon Sep 17 00:00:00 2001
> From: Carl Henrik Lunde <chlunde@...g.uio.no>
> Date: Wed, 25 Mar 2009 14:23:16 +0100
> Subject: [PATCH] blktrace: NUL-terminate user space messages
> 
> Make sure messages from user space are NUL-terminated strings,
> otherwise we could dump random memory to the block trace file.
> Additionally, I've limited the message to BLK_TN_MAX_MSG-1 characters,
> because the last character would be stripped by vscnprintf anyway.
> 
> Signed-off-by: Carl Henrik Lunde <chlunde@...g.uio.no>

Sure, i've picked up Carl's version of the fix instead, it dates 
back to early February!

( Li Zefan's fix was a tiny notch cleaner - i picked that cleanup up
  on top of Carl's patch separately. )

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/