[patch] xfs: check for underflow in xfs_iformat_fork()

[patch] xfs: check for underflow in xfs_iformat_fork()

[Dan Carpenter]

The "di_size" variable comes from the disk and it's a signed 64 bit.
We check the upper limit but we should check for negative numbers as
well.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
index 123971b..849fc70 100644
--- a/fs/xfs/xfs_inode_fork.c
+++ b/fs/xfs/xfs_inode_fork.c
@@ -167,7 +167,8 @@ xfs_iformat_fork(
 			}
 
 			di_size = be64_to_cpu(dip->di_size);
-			if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
+			if (unlikely(di_size < 0 ||
+				     di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
 				xfs_warn(ip->i_mount,
 			"corrupt inode %Lu (bad size %Ld for local inode).",
 					(unsigned long long) ip->i_ino,

Re: [patch] xfs: check for underflow in xfs_iformat_fork()

[Jeff Liu]

On 08/15/2013 01:53 PM, Dan Carpenter wrote:

> The "di_size" variable comes from the disk and it's a signed 64 bit.
> We check the upper limit but we should check for negative numbers as
> well.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> index 123971b..849fc70 100644
> --- a/fs/xfs/xfs_inode_fork.c
> +++ b/fs/xfs/xfs_inode_fork.c
> @@ -167,7 +167,8 @@ xfs_iformat_fork(
>  			}
>  
>  			di_size = be64_to_cpu(dip->di_size);
> -			if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
> +			if (unlikely(di_size < 0 ||

But the di_size is initialized to ZERO while allocating a new inode on disk.
I wonder if that is better to ASSERT in this case because the current check
is used to make sure that the item is inlined, or we don't need it at all.

> +				     di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
>  				xfs_warn(ip->i_mount,
>  			"corrupt inode %Lu (bad size %Ld for local inode).",
>  					(unsigned long long) ip->i_ino,
>

Thanks,
-Jeff

Re: [patch] xfs: check for underflow in xfs_iformat_fork()

[Ben Myers]

Hey Dan & Jeff,

On Thu, Aug 15, 2013 at 06:10:43PM +0800, Jeff Liu wrote:
> On 08/15/2013 01:53 PM, Dan Carpenter wrote:
> 
> > The "di_size" variable comes from the disk and it's a signed 64 bit.
> > We check the upper limit but we should check for negative numbers as
> > well.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > 
> > diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> > index 123971b..849fc70 100644
> > --- a/fs/xfs/xfs_inode_fork.c
> > +++ b/fs/xfs/xfs_inode_fork.c
> > @@ -167,7 +167,8 @@ xfs_iformat_fork(
> >  			}
> >  
> >  			di_size = be64_to_cpu(dip->di_size);
> > -			if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
> > +			if (unlikely(di_size < 0 ||
> 
> But the di_size is initialized to ZERO while allocating a new inode on disk.
> I wonder if that is better to ASSERT in this case because the current check
> is used to make sure that the item is inlined, or we don't need it at all.

Hmm.  Dan's additional check looks good to me.  In this case I'd say the forced
shutdown is more appropriate than an assert, because here we're reading the
inode from disk, as opposed to looking at a structure that is already incore
which we think we've initialized.  We want to handle unexpected inputs from
disk without crashing even if we are CONFIG_XFS_DEBUG.

How did you come across this one?

Reviewed-by: Ben Myers <bpm@sgi.com>

Regards,
Ben

Re: [patch] xfs: check for underflow in xfs_iformat_fork()

[Dan Carpenter]

On Thu, Aug 15, 2013 at 09:37:06AM -0500, Ben Myers wrote:
> Hey Dan & Jeff,
> 
> On Thu, Aug 15, 2013 at 06:10:43PM +0800, Jeff Liu wrote:
> > On 08/15/2013 01:53 PM, Dan Carpenter wrote:
> > 
> > > The "di_size" variable comes from the disk and it's a signed 64 bit.
> > > We check the upper limit but we should check for negative numbers as
> > > well.
> > > 
> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > 
> > > diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> > > index 123971b..849fc70 100644
> > > --- a/fs/xfs/xfs_inode_fork.c
> > > +++ b/fs/xfs/xfs_inode_fork.c
> > > @@ -167,7 +167,8 @@ xfs_iformat_fork(
> > >  			}
> > >  
> > >  			di_size = be64_to_cpu(dip->di_size);
> > > -			if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
> > > +			if (unlikely(di_size < 0 ||
> > 
> > But the di_size is initialized to ZERO while allocating a new inode on disk.
> > I wonder if that is better to ASSERT in this case because the current check
> > is used to make sure that the item is inlined, or we don't need it at all.
> 
> Hmm.  Dan's additional check looks good to me.  In this case I'd say the forced
> shutdown is more appropriate than an assert, because here we're reading the
> inode from disk, as opposed to looking at a structure that is already incore
> which we think we've initialized.  We want to handle unexpected inputs from
> disk without crashing even if we are CONFIG_XFS_DEBUG.
> 
> How did you come across this one?
> 

These are static checker things...  It's too false positive prone to
push on the real world yet.

regards,
dan carpenter

Re: [patch] xfs: check for underflow in xfs_iformat_fork()

[Dave Chinner]

On Thu, Aug 15, 2013 at 09:37:06AM -0500, Ben Myers wrote:
> Hey Dan & Jeff,
> 
> On Thu, Aug 15, 2013 at 06:10:43PM +0800, Jeff Liu wrote:
> > On 08/15/2013 01:53 PM, Dan Carpenter wrote:
> > 
> > > The "di_size" variable comes from the disk and it's a signed 64 bit.
> > > We check the upper limit but we should check for negative numbers as
> > > well.
> > > 
> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > 
> > > diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> > > index 123971b..849fc70 100644
> > > --- a/fs/xfs/xfs_inode_fork.c
> > > +++ b/fs/xfs/xfs_inode_fork.c
> > > @@ -167,7 +167,8 @@ xfs_iformat_fork(
> > >  			}
> > >  
> > >  			di_size = be64_to_cpu(dip->di_size);
> > > -			if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
> > > +			if (unlikely(di_size < 0 ||
> > 
> > But the di_size is initialized to ZERO while allocating a new inode on disk.
> > I wonder if that is better to ASSERT in this case because the current check
> > is used to make sure that the item is inlined, or we don't need it at all.
> 
> Hmm.  Dan's additional check looks good to me.  In this case I'd say the forced
> shutdown is more appropriate than an assert, because here we're reading the
> inode from disk, as opposed to looking at a structure that is already incore
> which we think we've initialized.  We want to handle unexpected inputs from
> disk without crashing even if we are CONFIG_XFS_DEBUG.

There are lots of places where we only check di_size to be greater
than some value, and don't check for it being less than zero. Hence
I think that a better solution might be to di_size unsigned as that
will catch "negative" sizes for all types of situations.

We've got the same problem in the userspace code as well and so
treating the size as unsigned will stop such validation problems
everywhere....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: [patch] xfs: check for underflow in xfs_iformat_fork()

[Ben Myers]

Dan,

On Fri, Aug 16, 2013 at 08:26:50AM +1000, Dave Chinner wrote:
> On Thu, Aug 15, 2013 at 09:37:06AM -0500, Ben Myers wrote:
> > Hey Dan & Jeff,
> > 
> > On Thu, Aug 15, 2013 at 06:10:43PM +0800, Jeff Liu wrote:
> > > On 08/15/2013 01:53 PM, Dan Carpenter wrote:
> > > 
> > > > The "di_size" variable comes from the disk and it's a signed 64 bit.
> > > > We check the upper limit but we should check for negative numbers as
> > > > well.
> > > > 
> > > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > > 
> > > > diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> > > > index 123971b..849fc70 100644
> > > > --- a/fs/xfs/xfs_inode_fork.c
> > > > +++ b/fs/xfs/xfs_inode_fork.c
> > > > @@ -167,7 +167,8 @@ xfs_iformat_fork(
> > > >  			}
> > > >  
> > > >  			di_size = be64_to_cpu(dip->di_size);
> > > > -			if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
> > > > +			if (unlikely(di_size < 0 ||
> > > 
> > > But the di_size is initialized to ZERO while allocating a new inode on disk.
> > > I wonder if that is better to ASSERT in this case because the current check
> > > is used to make sure that the item is inlined, or we don't need it at all.
> > 
> > Hmm.  Dan's additional check looks good to me.  In this case I'd say the forced
> > shutdown is more appropriate than an assert, because here we're reading the
> > inode from disk, as opposed to looking at a structure that is already incore
> > which we think we've initialized.  We want to handle unexpected inputs from
> > disk without crashing even if we are CONFIG_XFS_DEBUG.
> 
> There are lots of places where we only check di_size to be greater
> than some value, and don't check for it being less than zero. Hence
> I think that a better solution might be to di_size unsigned as that
> will catch "negative" sizes for all types of situations.

What do you say to making di_size unsigned?  Any interest?

Thanks,
Ben

Re: [patch] xfs: check for underflow in xfs_iformat_fork()

[Dan Carpenter]

On Fri, Aug 23, 2013 at 12:36:13PM -0500, Ben Myers wrote:
> Dan,
> 
> On Fri, Aug 16, 2013 at 08:26:50AM +1000, Dave Chinner wrote:
> > On Thu, Aug 15, 2013 at 09:37:06AM -0500, Ben Myers wrote:
> > > Hey Dan & Jeff,
> > > 
> > > On Thu, Aug 15, 2013 at 06:10:43PM +0800, Jeff Liu wrote:
> > > > On 08/15/2013 01:53 PM, Dan Carpenter wrote:
> > > > 
> > > > > The "di_size" variable comes from the disk and it's a signed 64 bit.
> > > > > We check the upper limit but we should check for negative numbers as
> > > > > well.
> > > > > 
> > > > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > > > 
> > > > > diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> > > > > index 123971b..849fc70 100644
> > > > > --- a/fs/xfs/xfs_inode_fork.c
> > > > > +++ b/fs/xfs/xfs_inode_fork.c
> > > > > @@ -167,7 +167,8 @@ xfs_iformat_fork(
> > > > >  			}
> > > > >  
> > > > >  			di_size = be64_to_cpu(dip->di_size);
> > > > > -			if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
> > > > > +			if (unlikely(di_size < 0 ||
> > > > 
> > > > But the di_size is initialized to ZERO while allocating a new inode on disk.
> > > > I wonder if that is better to ASSERT in this case because the current check
> > > > is used to make sure that the item is inlined, or we don't need it at all.
> > > 
> > > Hmm.  Dan's additional check looks good to me.  In this case I'd say the forced
> > > shutdown is more appropriate than an assert, because here we're reading the
> > > inode from disk, as opposed to looking at a structure that is already incore
> > > which we think we've initialized.  We want to handle unexpected inputs from
> > > disk without crashing even if we are CONFIG_XFS_DEBUG.
> > 
> > There are lots of places where we only check di_size to be greater
> > than some value, and don't check for it being less than zero. Hence
> > I think that a better solution might be to di_size unsigned as that
> > will catch "negative" sizes for all types of situations.
> 
> What do you say to making di_size unsigned?  Any interest?
> 

I'm not the right person to change "lots of places".  Some of these
are probably subtle.  Just give me the reported-by and I'm happy.

regards,
dan carpenter

Re: [patch] xfs: check for underflow in xfs_iformat_fork()

[Ben Myers]

Hey Dan,

On Mon, Aug 26, 2013 at 05:37:15PM +0300, Dan Carpenter wrote:
> On Fri, Aug 23, 2013 at 12:36:13PM -0500, Ben Myers wrote:
> > Dan,
> > 
> > On Fri, Aug 16, 2013 at 08:26:50AM +1000, Dave Chinner wrote:
> > > On Thu, Aug 15, 2013 at 09:37:06AM -0500, Ben Myers wrote:
> > > > Hey Dan & Jeff,
> > > > 
> > > > On Thu, Aug 15, 2013 at 06:10:43PM +0800, Jeff Liu wrote:
> > > > > On 08/15/2013 01:53 PM, Dan Carpenter wrote:
> > > > > 
> > > > > > The "di_size" variable comes from the disk and it's a signed 64 bit.
> > > > > > We check the upper limit but we should check for negative numbers as
> > > > > > well.
> > > > > > 
> > > > > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > > > > 
> > > > > > diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> > > > > > index 123971b..849fc70 100644
> > > > > > --- a/fs/xfs/xfs_inode_fork.c
> > > > > > +++ b/fs/xfs/xfs_inode_fork.c
> > > > > > @@ -167,7 +167,8 @@ xfs_iformat_fork(
> > > > > >  			}
> > > > > >  
> > > > > >  			di_size = be64_to_cpu(dip->di_size);
> > > > > > -			if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
> > > > > > +			if (unlikely(di_size < 0 ||
> > > > > 
> > > > > But the di_size is initialized to ZERO while allocating a new inode on disk.
> > > > > I wonder if that is better to ASSERT in this case because the current check
> > > > > is used to make sure that the item is inlined, or we don't need it at all.
> > > > 
> > > > Hmm.  Dan's additional check looks good to me.  In this case I'd say the forced
> > > > shutdown is more appropriate than an assert, because here we're reading the
> > > > inode from disk, as opposed to looking at a structure that is already incore
> > > > which we think we've initialized.  We want to handle unexpected inputs from
> > > > disk without crashing even if we are CONFIG_XFS_DEBUG.
> > > 
> > > There are lots of places where we only check di_size to be greater
> > > than some value, and don't check for it being less than zero. Hence
> > > I think that a better solution might be to di_size unsigned as that
> > > will catch "negative" sizes for all types of situations.
> > 
> > What do you say to making di_size unsigned?  Any interest?
> > 
> 
> I'm not the right person to change "lots of places".  Some of these
> are probably subtle.  Just give me the reported-by and I'm happy.

I'll apply this for now, and we'll see if someone is interested enough to pick
up the rest.

Thanks,
	Ben