[PATCH 17/21] fat: Fix _fat_bmap() race

[OGAWA Hirofumi]

fat_get_cluster() assumes the requested blocknr isn't truncated during
read. _fat_bmap() doesn't follow this rule.

This protects it by ->i_mutex.

Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
---

 fs/fat/inode.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff -puN fs/fat/inode.c~fat_fat_bmap-fix fs/fat/inode.c
--- linux-2.6/fs/fat/inode.c~fat_fat_bmap-fix	2008-09-14 05:25:34.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/inode.c	2008-09-14 06:28:26.000000000 +0900
@@ -199,7 +199,14 @@ static ssize_t fat_direct_IO(int rw, str
 
 static sector_t _fat_bmap(struct address_space *mapping, sector_t block)
 {
-	return generic_block_bmap(mapping, block, fat_get_block);
+	sector_t blocknr;
+
+	/* fat_get_cluster() assumes the requested blocknr isn't truncated. */
+	mutex_lock(&mapping->host->i_mutex);
+	blocknr = generic_block_bmap(mapping, block, fat_get_block);
+	mutex_unlock(&mapping->host->i_mutex);
+
+	return blocknr;
 }
 
 static const struct address_space_operations fat_aops = {
_
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