linux-ext4 - [PATCH] ext4: Only zero partial blocks in ext4_zero_partial

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1371719673-3033-1-git-send-email-lczerner@redhat.com>
Date:	Thu, 20 Jun 2013 11:14:33 +0200
From:	Lukas Czerner <lczerner@...hat.com>
To:	linux-ext4@...r.kernel.org
Cc:	tytso@....edu, Lukas Czerner <lczerner@...hat.com>
Subject: [PATCH] ext4: Only zero partial blocks in ext4_zero_partial_blocks()

Currently if we pass range into ext4_zero_partial_blocks() which covers
entire block we would attempt to zero it even though we should only zero
unaligned part of the block.

Fix this by checking whether the range covers the whole block skip
zeroing if so.

Signed-off-by: Lukas Czerner <lczerner@...hat.com>
---
 fs/ext4/inode.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3acf353..ce9f926 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3698,33 +3698,36 @@ int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
 {
 	struct super_block *sb = inode->i_sb;
 	struct address_space *mapping = inode->i_mapping;
-	unsigned partial = lstart & (sb->s_blocksize - 1);
+	unsigned partial_start, partial_end;
 	ext4_fsblk_t start, end;
 	loff_t byte_end = (lstart + length - 1);
 	int err = 0;
 
+	partial_start = lstart & (sb->s_blocksize - 1);
+	partial_end = byte_end & (sb->s_blocksize - 1);
+
 	start = lstart >> sb->s_blocksize_bits;
 	end = byte_end >> sb->s_blocksize_bits;
 
 	/* Handle partial zero within the single block */
-	if (start == end) {
+	if (start == end &&
+	    (partial_start || (partial_end != sb->s_blocksize - 1))) {
 		err = ext4_block_zero_page_range(handle, mapping,
 						 lstart, length);
 		return err;
 	}
 	/* Handle partial zero out on the start of the range */
-	if (partial) {
+	if (partial_start) {
 		err = ext4_block_zero_page_range(handle, mapping,
 						 lstart, sb->s_blocksize);
 		if (err)
 			return err;
 	}
 	/* Handle partial zero out on the end of the range */
-	partial = byte_end & (sb->s_blocksize - 1);
-	if (partial != sb->s_blocksize - 1)
+	if (partial_end != sb->s_blocksize - 1)
 		err = ext4_block_zero_page_range(handle, mapping,
-						 byte_end - partial,
-						 partial + 1);
+						 byte_end - partial_end,
+						 partial_end + 1);
 	return err;
 }
 
-- 
1.8.2.1

--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html