fat: mmu_private race fix
mmu_private is 64bits value, hence it's not atomic to update.
So, the access rule for mmu_private is we must hold ->i_mutex. But,
fat_get_block() path doesn't follow the rule on non-allocation path.
This fixes by using i_size instead if non-allocation path.
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index 589edde..b426022 100644
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -293,10 +293,12 @@
}
int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
- unsigned long *mapped_blocks)
+ unsigned long *mapped_blocks, int create)
{
struct super_block *sb = inode->i_sb;
struct msdos_sb_info *sbi = MSDOS_SB(sb);
+ const unsigned long blocksize = sb->s_blocksize;
+ const unsigned char blocksize_bits = sb->s_blocksize_bits;
sector_t last_block;
int cluster, offset;
@@ -309,10 +311,21 @@
}
return 0;
}
- last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
- >> sb->s_blocksize_bits;
- if (sector >= last_block)
- return 0;
+
+ last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
+ if (sector >= last_block) {
+ if (!create)
+ return 0;
+
+ /*
+ * ->mmu_private can access on only allocation path.
+ * (caller must hold ->i_mutex)
+ */
+ last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
+ >> blocksize_bits;
+ if (sector >= last_block)
+ return 0;
+ }
cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
offset = sector & (sbi->sec_per_clus - 1);