diff mbox series

NFS: fs_context: validate UDP retrans to prevent shift out-of-bounds

Message ID 20210302001930.2253-1-rdunlap@infradead.org (mailing list archive)
State New
Headers show
Series NFS: fs_context: validate UDP retrans to prevent shift out-of-bounds | expand

Commit Message

Randy Dunlap March 2, 2021, 12:19 a.m. UTC
Fix shift out-of-bounds in xprt_calc_majortimeo(). This is caused
by a garbage timeout (retrans) mount option being passed to nfs mount,
in this case from syzkaller.

If the protocol is XPRT_TRANSPORT_UDP, then 'retrans' is a shift
value for a 64-bit long integer, so 'retrans' cannot be >= 64.
If it is >= 64, fail the mount and return an error.

Fixes: 9954bf92c0cd ("NFS: Move mount parameterisation bits into their own file")
Reported-by: syzbot+ba2e91df8f74809417fa@syzkaller.appspotmail.com
Reported-by: syzbot+f3a0fa110fd630ab56c8@syzkaller.appspotmail.com
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: linux-nfs@vger.kernel.org
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
---
 fs/nfs/fs_context.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

Randy Dunlap March 16, 2021, 10:35 p.m. UTC | #1
ping?

On 3/1/21 4:19 PM, Randy Dunlap wrote:
> Fix shift out-of-bounds in xprt_calc_majortimeo(). This is caused
> by a garbage timeout (retrans) mount option being passed to nfs mount,
> in this case from syzkaller.
> 
> If the protocol is XPRT_TRANSPORT_UDP, then 'retrans' is a shift
> value for a 64-bit long integer, so 'retrans' cannot be >= 64.
> If it is >= 64, fail the mount and return an error.
> 
> Fixes: 9954bf92c0cd ("NFS: Move mount parameterisation bits into their own file")
> Reported-by: syzbot+ba2e91df8f74809417fa@syzkaller.appspotmail.com
> Reported-by: syzbot+f3a0fa110fd630ab56c8@syzkaller.appspotmail.com
> Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
> Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
> Cc: Anna Schumaker <anna.schumaker@netapp.com>
> Cc: linux-nfs@vger.kernel.org
> Cc: David Howells <dhowells@redhat.com>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: stable@vger.kernel.org
> ---
>  fs/nfs/fs_context.c |   12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> --- lnx-512-rc1.orig/fs/nfs/fs_context.c
> +++ lnx-512-rc1/fs/nfs/fs_context.c
> @@ -974,6 +974,15 @@ static int nfs23_parse_monolithic(struct
>  			       sizeof(mntfh->data) - mntfh->size);
>  
>  		/*
> +		 * for proto == XPRT_TRANSPORT_UDP, which is what uses
> +		 * to_exponential, implying shift: limit the shift value
> +		 * to BITS_PER_LONG (majortimeo is unsigned long)
> +		 */
> +		if (!(data->flags & NFS_MOUNT_TCP)) /* this will be UDP */
> +			if (data->retrans >= 64) /* shift value is too large */
> +				goto out_invalid_data;
> +
> +		/*
>  		 * Translate to nfs_fs_context, which nfs_fill_super
>  		 * can deal with.
>  		 */
> @@ -1073,6 +1082,9 @@ out_no_address:
>  
>  out_invalid_fh:
>  	return nfs_invalf(fc, "NFS: invalid root filehandle");
> +
> +out_invalid_data:
> +	return nfs_invalf(fc, "NFS: invalid binary mount data");
>  }
>  
>  #if IS_ENABLED(CONFIG_NFS_V4)
>
Trond Myklebust March 16, 2021, 11:19 p.m. UTC | #2
Hi Randy,

On Tue, 2021-03-16 at 15:35 -0700, Randy Dunlap wrote:
> ping?
> 

I can take this patch for the next merge window.

> On 3/1/21 4:19 PM, Randy Dunlap wrote:
> > Fix shift out-of-bounds in xprt_calc_majortimeo(). This is caused
> > by a garbage timeout (retrans) mount option being passed to nfs
> > mount,
> > in this case from syzkaller.
> > 
> > If the protocol is XPRT_TRANSPORT_UDP, then 'retrans' is a shift
> > value for a 64-bit long integer, so 'retrans' cannot be >= 64.
> > If it is >= 64, fail the mount and return an error.
> > 
> > Fixes: 9954bf92c0cd ("NFS: Move mount parameterisation bits into
> > their own file")
> > Reported-by: syzbot+ba2e91df8f74809417fa@syzkaller.appspotmail.com
> > Reported-by: syzbot+f3a0fa110fd630ab56c8@syzkaller.appspotmail.com
> > Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
> > Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
> > Cc: Anna Schumaker <anna.schumaker@netapp.com>
> > Cc: linux-nfs@vger.kernel.org
> > Cc: David Howells <dhowells@redhat.com>
> > Cc: Al Viro <viro@zeniv.linux.org.uk>
> > Cc: stable@vger.kernel.org
> > ---
> >  fs/nfs/fs_context.c |   12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> > 
> > --- lnx-512-rc1.orig/fs/nfs/fs_context.c
> > +++ lnx-512-rc1/fs/nfs/fs_context.c
> > @@ -974,6 +974,15 @@ static int nfs23_parse_monolithic(struct
> >                                sizeof(mntfh->data) - mntfh->size);
> >  
> >                 /*
> > +                * for proto == XPRT_TRANSPORT_UDP, which is what
> > uses
> > +                * to_exponential, implying shift: limit the shift
> > value
> > +                * to BITS_PER_LONG (majortimeo is unsigned long)
> > +                */
> > +               if (!(data->flags & NFS_MOUNT_TCP)) /* this will be
> > UDP */
> > +                       if (data->retrans >= 64) /* shift value is
> > too large */
> > +                               goto out_invalid_data;
> > +
> > +               /*
> >                  * Translate to nfs_fs_context, which
> > nfs_fill_super
> >                  * can deal with.
> >                  */
> > @@ -1073,6 +1082,9 @@ out_no_address:
> >  
> >  out_invalid_fh:
> >         return nfs_invalf(fc, "NFS: invalid root filehandle");
> > +
> > +out_invalid_data:
> > +       return nfs_invalf(fc, "NFS: invalid binary mount data");
> >  }
> >  
> >  #if IS_ENABLED(CONFIG_NFS_V4)
> > 
> 
>
diff mbox series

Patch

--- lnx-512-rc1.orig/fs/nfs/fs_context.c
+++ lnx-512-rc1/fs/nfs/fs_context.c
@@ -974,6 +974,15 @@  static int nfs23_parse_monolithic(struct
 			       sizeof(mntfh->data) - mntfh->size);
 
 		/*
+		 * for proto == XPRT_TRANSPORT_UDP, which is what uses
+		 * to_exponential, implying shift: limit the shift value
+		 * to BITS_PER_LONG (majortimeo is unsigned long)
+		 */
+		if (!(data->flags & NFS_MOUNT_TCP)) /* this will be UDP */
+			if (data->retrans >= 64) /* shift value is too large */
+				goto out_invalid_data;
+
+		/*
 		 * Translate to nfs_fs_context, which nfs_fill_super
 		 * can deal with.
 		 */
@@ -1073,6 +1082,9 @@  out_no_address:
 
 out_invalid_fh:
 	return nfs_invalf(fc, "NFS: invalid root filehandle");
+
+out_invalid_data:
+	return nfs_invalf(fc, "NFS: invalid binary mount data");
 }
 
 #if IS_ENABLED(CONFIG_NFS_V4)