svn commit: r328479 - in head/sys: fs/ext2fs ufs/ufs

[Konstantin Belousov]

On Sat, Jan 27, 2018 at 03:33:52PM +0000, Pedro F. Giffuni wrote:
> Author: pfg
> Date: Sat Jan 27 15:33:52 2018
> New Revision: 328479
> URL: https://svnweb.freebsd.org/changeset/base/328479
> 
> Log:
>   {ext2|ufs}_readdir: Set limit on valid ncookies values.
>   
>   Sanitize the values that will be assigned to ncookies so that we ensure
>   they are sane and we can handle them.
>   
>   Let ncookies signed as it was before r328346. The valid range is such
>   that unsigned values are not required and we are not able to avoid at
>   least one cast anyways.
>   
>   Hinted by:	bde
> 
> Modified:
>   head/sys/fs/ext2fs/ext2_lookup.c
>   head/sys/ufs/ufs/ufs_vnops.c
> 
> Modified: head/sys/fs/ext2fs/ext2_lookup.c
> ==============================================================================
> --- head/sys/fs/ext2fs/ext2_lookup.c	Sat Jan 27 13:46:55 2018	(r328478)
> +++ head/sys/fs/ext2fs/ext2_lookup.c	Sat Jan 27 15:33:52 2018	(r328479)
> @@ -145,14 +145,18 @@ ext2_readdir(struct vop_readdir_args *ap)
>  	off_t offset, startoffset;
>  	size_t readcnt, skipcnt;
>  	ssize_t startresid;
> -	u_int ncookies;
> +	int ncookies;
>  	int DIRBLKSIZ = VTOI(ap->a_vp)->i_e2fs->e2fs_bsize;
>  	int error;
>  
>  	if (uio->uio_offset < 0)
>  		return (EINVAL);
>  	ip = VTOI(vp);
> +	if (uio->uio_resid < 0)
> +		uio->uio_resid = 0;
>  	if (ap->a_ncookies != NULL) {
> +		if (uio->uio_resid > MAXPHYS)
> +			uio->uio_resid = MAXPHYS;
>  		ncookies = uio->uio_resid;
>  		if (uio->uio_offset >= ip->i_size)
>  			ncookies = 0;
> 
> Modified: head/sys/ufs/ufs/ufs_vnops.c
> ==============================================================================
> --- head/sys/ufs/ufs/ufs_vnops.c	Sat Jan 27 13:46:55 2018	(r328478)
> +++ head/sys/ufs/ufs/ufs_vnops.c	Sat Jan 27 15:33:52 2018	(r328479)
> @@ -2170,7 +2170,7 @@ ufs_readdir(ap)
>  	off_t offset, startoffset;
>  	size_t readcnt, skipcnt;
>  	ssize_t startresid;
> -	u_int ncookies;
> +	int ncookies;
>  	int error;
>  
>  	if (uio->uio_offset < 0)
> @@ -2178,7 +2178,11 @@ ufs_readdir(ap)
>  	ip = VTOI(vp);
>  	if (ip->i_effnlink == 0)
>  		return (0);
> +	if (uio->uio_resid < 0)
> +		uio->uio_resid = 0;
>  	if (ap->a_ncookies != NULL) {
> +		if (uio->uio_resid > MAXPHYS)
> +			uio->uio_resid = MAXPHYS;
You just break nfs server.

Look at nfsrvd_readdir() call to VOP_READDIR.  Almost all code which calls
VOP_READDIR() memoize the value of uio_resid before and after the call and
interpret the difference as the amount of data returned.

I said above that only nfs server is broken, because only the server uses
cookies, otherwise your patch would break everything.

>  		ncookies = uio->uio_resid;
>  		if (uio->uio_offset >= ip->i_size)
>  			ncookies = 0;