Re: [patch 1/9] fs: libfs buffered write leak fix

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, 29 Jan 2007 11:31:46 +0100 (CET)
Nick Piggin <npiggin@xxxxxxx> wrote:

> simple_prepare_write and nobh_prepare_write leak uninitialised kernel data.

They do?  Under what situation?

> Fix the former,

How?

> make a note of the latter. Several other filesystems seem
> to be iffy here, too.

Please, tell us what the bug is so that others have a chance of reviewing
and, if needed, fixing those other filesystems.

> --- linux-2.6.orig/fs/libfs.c
> +++ linux-2.6/fs/libfs.c
> @@ -327,32 +327,35 @@ int simple_readpage(struct file *file, s
>  int simple_prepare_write(struct file *file, struct page *page,
>  			unsigned from, unsigned to)
>  {
> -	if (!PageUptodate(page)) {
> -		if (to - from != PAGE_CACHE_SIZE) {
> -			void *kaddr = kmap_atomic(page, KM_USER0);
> -			memset(kaddr, 0, from);
> -			memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
> -			flush_dcache_page(page);
> -			kunmap_atomic(kaddr, KM_USER0);
> -		}
> +	if (PageUptodate(page))
> +		return 0;
> +
> +	if (to - from != PAGE_CACHE_SIZE) {
> +		clear_highpage(page);
> +		flush_dcache_page(page);
>  		SetPageUptodate(page);
>  	}

memclear_highpage_flush() is fashionable.

> ===================================================================
> --- linux-2.6.orig/fs/buffer.c
> +++ linux-2.6/fs/buffer.c
> @@ -2344,6 +2344,8 @@ int nobh_prepare_write(struct page *page
>  
>  	if (is_mapped_to_disk)
>  		SetPageMappedToDisk(page);
> +
> +	/* XXX: information leak vs read(2) */
>  	SetPageUptodate(page);
>  
>  	/*

That comment is too terse to be useful.
-
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux