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

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Message-Id: <12011815300568720b5d1587bb777fed0d5b016f0854@nudt.edu.cn>
Date:	Wed, 18 Jan 2012 15:30:05 +0800
From:	"Li Wang" <liwang@...t.edu.cn>
To:	ecryptfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] eCryptfs: infinite loop bug

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.

Cheers,
Li Wang

---

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

--- read_write.c.orig 2012-01-18 10:39:26.000000000 +0800
+++ read_write.c 2012-01-18 19:48:41.484196221 +0800
@@ -130,7 +130,7 @@ 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;



--- read_write.c.orig	2012-01-18 10:39:26.000000000 +0800
+++ read_write.c	2012-01-18 19:48:41.484196221 +0800
@@ -130,7 +130,7 @@ 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;