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);
diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 140fc39..2ecaa17 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -77,7 +77,7 @@
*bh = NULL;
iblock = *pos >> sb->s_blocksize_bits;
- err = fat_bmap(dir, iblock, &phys, &mapped_blocks);
+ err = fat_bmap(dir, iblock, &phys, &mapped_blocks, 0);
if (err || !phys)
return -1; /* beyond EOF or error */
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index a69f7f9..4efc503 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -91,7 +91,9 @@
/* for avoiding the race between fat_free() and fat_get_cluster() */
unsigned int cache_valid_id;
- loff_t mmu_private;
+ /* NOTE: mmu_private is 64bits, so must hold ->i_mutex to access */
+ loff_t mmu_private; /* physically allocated size */
+
int i_start; /* first cluster or 0 */
int i_logstart; /* logical first cluster */
int i_attrs; /* unused attribute bits */
@@ -222,7 +224,7 @@
extern int fat_get_cluster(struct inode *inode, int cluster,
int *fclus, int *dclus);
extern int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
- unsigned long *mapped_blocks);
+ unsigned long *mapped_blocks, int create);
/* fat/dir.c */
extern const struct file_operations fat_dir_operations;
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index be88208..9e37ad9 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -64,7 +64,7 @@
sector_t phys;
int err, offset;
- err = fat_bmap(inode, iblock, &phys, &mapped_blocks);
+ err = fat_bmap(inode, iblock, &phys, &mapped_blocks, create);
if (err)
return err;
if (phys) {
@@ -94,7 +94,7 @@
*max_blocks = min(mapped_blocks, *max_blocks);
MSDOS_I(inode)->mmu_private += *max_blocks << sb->s_blocksize_bits;
- err = fat_bmap(inode, iblock, &phys, &mapped_blocks);
+ err = fat_bmap(inode, iblock, &phys, &mapped_blocks, create);
if (err)
return err;