lkml.org 
[lkml]   [2009]   [Oct]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2 1/1]: fs: pipe.c null pointer dereference + sign off
From
Date
On Mon, 2009-10-19 at 11:13 -0700, Earl Chew wrote:
> [ Exactly as before, but with sign off ]
>

You've got a few more submission related issues, see below.

> This patch fixes a null pointer exception in pipe_rdwr_open() which
> generates the stack trace:
>
>
> > Unable to handle kernel NULL pointer dereference at 0000000000000028 RIP:
> > [<ffffffff802899a5>] pipe_rdwr_open+0x35/0x70
> > [<ffffffff8028125c>] __dentry_open+0x13c/0x230
> > [<ffffffff8028143d>] do_filp_open+0x2d/0x40
> > [<ffffffff802814aa>] do_sys_open+0x5a/0x100
> > [<ffffffff8021faf3>] sysenter_do_call+0x1b/0x67
>
> This defect is also described in:
> http://lkml.org/lkml/2009/10/14/184
> http://bugzilla.kernel.org/show_bug.cgi?id=14416
>
>
> The failure mode is triggered by an attempt to open an anonymous
> pipe via /proc/pid/fd/* as exemplified by this script:
>
> =============================================================
> #!/bin/sh
> while : ; do
> { echo y ; sleep 1 ; } | { while read ; do echo z$REPLY; done ; } &
> PID=$!
> OUT=$(ps -efl | grep 'sleep 1' | grep -v grep |
> { read PID REST ; echo $PID; } )
> OUT="${OUT%% *}"
> DELAY=$((RANDOM * 1000 / 32768))
> usleep $((DELAY * 1000 + RANDOM % 1000 ))
> echo n > /proc/$OUT/fd/1 # Trigger defect
> done
> =============================================================
>
> Note that the failure window is quite small and I could only
> reliably reproduce the defect by inserting a small delay
> in pipe_rdwr_open(). For example:
>
> static int
> pipe_rdwr_open(struct inode *inode, struct file *filp)
> {
> msleep(100);
> mutex_lock(&inode->i_mutex);
>
>
> Although the defect was observed in pipe_rdwr_open(), I think it
> makes sense to replicate the change through all the pipe_*_open()
> functions.
>
> The core of the change is to verify that inode->i_pipe has not
> been released before attempting to manipulate it. If inode->i_pipe
> is no longer present, return ENOENT to indicate so.
>
> The comment about potentially using atomic_t for i_pipe->readers
> and i_pipe->writers has also been removed because it is no longer
> relevant in this context. The inode->i_mutex lock must be used so
> that inode->i_pipe can be dealt with correctly.
>
>
> Signed-off-by: Earl Chew <earl_chew@agilent.com>
>
>
> --- linux-2.6.21_mvlcge500/fs/pipe.c.orig 2009-10-15
> 20:33:53.000000000 -0700
> +++ linux-2.6.21_mvlcge500/fs/pipe.c 2009-10-15 21:21:25.000000000 -0700
> @@ -712,36 +712,55 @@ pipe_rdwr_release(struct inode *inode, s
> static int

You patch looks like it might be line wrapped .. Sometimes mailers will
do that if you don't tell them the content is already formatted.

Also I see your using a MontaVista kernel, which is older than current
mainline .. I would assume you tested this on a recent kernel also?

> pipe_read_open(struct inode *inode, struct file *filp)
> {
> - /* We could have perhaps used atomic_t, but this and friends
> - below are the only places. So it doesn't seem worthwhile. */
> + int ret = -ENOENT;

>From checkpatch,

ERROR: code indent should use tabs where possible
#125: FILE: fs/pipe.c:720:
+ ret = 0;$

It looks like maybe your mailer (or copy and paste) may have stripped
all the tabs off your patch. This makes is very difficult to apply.


Daniel



\
 
 \ /
  Last update: 2009-10-19 21:45    [W:0.069 / U:4.268 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site