linux-kernel - Re: [PATCH] generic compat_sys

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Message-ID: <4926F21D.7030709@sandeen.net>
Date:	Fri, 21 Nov 2008 11:38:37 -0600
From:	Eric Sandeen <sandeen@...deen.net>
To:	Christoph Hellwig <hch@....de>
CC:	linux-kernel@...r.kernel.org, davem@...emloft.net,
	tony.luck@...el.com, ralf@...ux-mips.org, kyle@...artin.ca,
	schwidefsky@...ibm.com
Subject: Re: [PATCH] generic compat_sys_ustat

Christoph Hellwig wrote:
> Due to a different size of ino_t ustat needs a compat handler, but
> currently only x86 and mips provide one.  Add a generic compat_sys_ustat
> and switch all architectures over to it.
> 
> Found by Eric Sandeen when running xfstests/017 on ppc64, which causes
> stack smashing warnings on RHEL/Fedora due to the too large amount of
> data writen by the syscall.

...

> Index: linux-2.6/fs/compat.c
> ===================================================================
> --- linux-2.6.orig/fs/compat.c	2008-11-20 20:09:52.000000000 +0100
> +++ linux-2.6/fs/compat.c	2008-11-20 20:16:05.000000000 +0100
> @@ -378,6 +378,24 @@ out:
>  	return error;
>  }
>  
> +asmlinkage long compat_sys_ustat(unsigned dev, struct compat_ustat __user *u32)

Oh, I had also suggested that the use of "u32" here was slightly
confusing, it at least made me do a double-take with the unsigned 32 bit
type... not a big deal, but just thought I'd mention it.

Thanks,
-Eric

> +{
> +	struct ustat *u = compat_alloc_user_space(sizeof(*u));
> +	int ret;
> +
> +	ret = sys_ustat(dev, u);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (!access_ok(VERIFY_WRITE, u32, sizeof(*u32)) ||
> +	    __put_user((compat_daddr_t) u->f_tfree, &u32->f_tfree) ||
> +	    __put_user((compat_ino_t) u->f_tinode, &u32->f_tfree) ||
> +	    __copy_to_user(&u32->f_fname, u->f_fname, sizeof(u32->f_fname)) ||
> +	    __copy_to_user(&u32->f_fpack, u->f_fpack, sizeof(u32->f_fpack)))
> +		return -EFAULT;
> +	return 0;
> +}
> +
--
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