Patchwork [1/1] eCryptfs: Infinite loop due to overflow in ecryptfs_write()

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Submitter Colin King
Date March 5, 2012, 5:18 p.m.
Message ID <1330967908-12382-2-git-send-email-colin.king@canonical.com>
Download mbox | patch
Permalink /patch/144719/
State New
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Comments

Colin King - March 5, 2012, 5:18 p.m.
From: Colin Ian King <colin.king@canonical.com>

BugLink: http://bugs.launchpad.net/bugs/947143

ecryptfs_write() can enter an infinite loop when truncating a file to a
size larger than 4G. This only happens on architectures where size_t is
represented by 32 bits.

This was caused by a size_t overflow due to it incorrectly being used to
store the result of a calculation which uses potentially large values of
type loff_t.

[tyhicks@canonical.com: rewrite subject and commit message]
Signed-off-by: Li Wang <liwang@nudt.edu.cn>
Signed-off-by: Yunchuan Wen <wenyunchuan@kylinos.com.cn>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
(backported from commit 684a3ff7e69acc7c678d1a1394fe9e757993fd34)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 fs/ecryptfs/read_write.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

Patch

diff --git a/fs/ecryptfs/read_write.c b/fs/ecryptfs/read_write.c
index 54eb14c..608c1c3 100644
--- a/fs/ecryptfs/read_write.c
+++ b/fs/ecryptfs/read_write.c
@@ -130,7 +130,7 @@  int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
 		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 (fatal_signal_pending(current)) {
 			rc = -EINTR;
@@ -141,7 +141,7 @@  int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
 			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;