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SubjectRe: [PATCH] blktrace: fix a bug in blk_msg_write()
On Fri, Apr 03 2009, Ingo Molnar wrote:
>
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> >
> > * Jens Axboe <jens.axboe@oracle.com> wrote:
> >
> > > On Fri, Apr 03 2009, Ingo Molnar wrote:
> > > >
> > > > * Li Zefan <lizf@cn.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@cn.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@kernel.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@ping.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@ping.uio.no>
> >
> > Sure, i've picked up Carl's version of the fix instead, it dates
> > back to early February!
>
> I've also checked the linux-btrace archives a few months back and
> nothing else seems to be missing - are you aware of any other
> missing items?

Nope, I think Carls patch was the only pending thing I had from the
archives.

--
Jens Axboe



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