linux-kernel - [PATCH] hfsplus: fix concurrent acess of alloc

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Date:	Mon, 17 Feb 2014 14:20:47 +0200
From:	Sougata Santra <sougata@...era.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Christoph Hellwig <hch@....de>, <linux-fsdevel@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Vyacheslav Dubeyko <slava@...eyko.com>,
	"Joe Perches" <joe@...ches.com>,
	Alexey Khoroshilov <khoroshilov@...ras.ru>
Subject: [PATCH] hfsplus: fix concurrent acess of alloc_blocks


Concurrent access to alloc_blocks in hfsplus_inode_info is
protected by extents_lock mutex. This patch fixes two
instances where alloc_blocks modification was not protected
with this lock. This fixes possible allocation bitmap
corruption in race conditions while extending and truncating
files.

Signed-off-by: Sougata Santra <sougata@...era.com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 fs/hfsplus/extents.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c
index fbb212f..314c858 100644
--- a/fs/hfsplus/extents.c
+++ b/fs/hfsplus/extents.c
@@ -498,11 +498,13 @@ int hfsplus_file_extend(struct inode *inode)
 			goto insert_extent;
 	}
 out:
-	mutex_unlock(&hip->extents_lock);
 	if (!res) {
 		hip->alloc_blocks += len;
+		mutex_unlock(&hip->extents_lock);
 		hfsplus_mark_inode_dirty(inode, HFSPLUS_I_ALLOC_DIRTY);
+		return 0;
 	}
+	mutex_unlock(&hip->extents_lock);
 	return res;
 
 insert_extent:
@@ -592,9 +594,9 @@ void hfsplus_file_truncate(struct inode *inode)
 		hfs_brec_remove(&fd);
 	}
 	hfs_find_exit(&fd);
-	mutex_unlock(&hip->extents_lock);
 
 	hip->alloc_blocks = blk_cnt;
+	mutex_unlock(&hip->extents_lock);
 out:
 	hip->phys_size = inode->i_size;
 	hip->fs_blocks = (inode->i_size + sb->s_blocksize - 1) >>
-- 
1.8.1.4



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