linux-kernel - Re:Re: [PATCH] eCryptfs: infinite loop bug

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Message-Id: <12011909443668a7a65ff897afc93db177848236f08f@nudt.edu.cn>
Date:	Thu, 19 Jan 2012 09:44:36 +0800
From:	"Li Wang" <liwang@...t.edu.cn>
To:	ecryptfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Dustin Kirkland" <kirkland@...onical.com>,
	"Cong Wang" <xiyou.wangcong@...il.com>,
	"Tyler Hicks" <tyhicks@...onical.com>
Subject: Re:Re: [PATCH] eCryptfs: infinite loop bug



Hi,
  Thanks Cong Wang for the kind reminding regarding the patch format.
  We did notice that the total_remaining_zeroes need be revised as well, 
and the start_offset_in_page, num_bytes need not be revised (always smaller 
than PAGE_CACHE_SIZE, even the huge page size is supported, 
the 4G page size is not present in the current world?)
but we forget to include the revision for total_remaining_zeroes, so here comes the patch.

Cheers,
Li Wang

Signed-off-by: Li Wang <liwang@...t.edu.cn>
               Yunchuan Wen <wenyunchuan@...inos.com.cn>

---

--- a/fs/ecryptfs/read_write.c	2012-01-19 17:34:54.666940824 +0800
+++ b/fs/ecryptfs/read_write.c	2012-01-19 17:35:16.257940840 +0800
@@ -130,13 +130,13 @@ int ecryptfs_write(struct inode *ecryptf
 		pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 		size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 		size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
-		size_t total_remaining_bytes = ((offset + size) - pos);
+		loff_t total_remaining_bytes = ((offset + size) - pos);
 
 		if (num_bytes > total_remaining_bytes)
 			num_bytes = total_remaining_bytes;
 		if (pos < offset) {
 			/* remaining zeros to write, up to destination offset */
-			size_t total_remaining_zeros = (offset - pos);
+			loff_t total_remaining_zeros = (offset - pos);
 
 			if (num_bytes > total_remaining_zeros)
 				num_bytes = total_remaining_zeros;





---------- Origin message ----------
>From："Tyler Hicks" <tyhicks@...onical.com>
>To："Cong Wang" <xiyou.wangcong@...il.com>
>Subject：Re: [PATCH] eCryptfs: infinite loop bug
>Date：2012-01-19 05:40:51

On 2012-01-18 23:26:52, Cong Wang wrote:
> On 01/18/2012 03:30 PM, Li Wang wrote:
> >Hi,
> > There is an infinite loop bug in eCryptfs, to make it present,
> >just truncate to generate a huge file (>= 4G) on a 32-bit machine
> >under the plain text foleder mounted with eCryptfs, a simple command
> >'truncate -s 4G dummy' is enough. Note: 4GB is smaller than 4G,
> >therefore the following command 'truncate -s 4GB dummy' will not trigger this bug.
> >The bug comes from a data overflow, the patch below fixes it.
> >
> >
>
> Hi,
>
> Your patch is not correctly generated, you need to make the diff on
> top of the source tree.
>
> Also, after reviewing the code, I think there are more places need
> to fix. Can you try my patch below?