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Subject[PATCH 3.18 079/145] fat: fix using uninitialized fields of fat_inode/fsinfo_inode
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

commit c0d0e351285161a515396b7b1ee53ec9ffd97e3c upstream.

Recently fallocate patch was merged and it uses
MSDOS_I(inode)->mmu_private at fat_evict_inode(). However,
fat_inode/fsinfo_inode that was introduced in past didn't initialize
MSDOS_I(inode) properly.

With those combinations, it became the cause of accessing random entry
in FAT area.

Link: http://lkml.kernel.org/r/87pohrj4i8.fsf@mail.parknet.co.jp
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Reported-by: Moreno Bartalucci <moreno.bartalucci@tecnorama.it>
Tested-by: Moreno Bartalucci <moreno.bartalucci@tecnorama.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/fat/inode.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1266,6 +1266,16 @@ out:
return 0;
}

+static void fat_dummy_inode_init(struct inode *inode)
+{
+ /* Initialize this dummy inode to work as no-op. */
+ MSDOS_I(inode)->mmu_private = 0;
+ MSDOS_I(inode)->i_start = 0;
+ MSDOS_I(inode)->i_logstart = 0;
+ MSDOS_I(inode)->i_attrs = 0;
+ MSDOS_I(inode)->i_pos = 0;
+}
+
static int fat_read_root(struct inode *inode)
{
struct super_block *sb = inode->i_sb;
@@ -1711,12 +1721,13 @@ int fat_fill_super(struct super_block *s
fat_inode = new_inode(sb);
if (!fat_inode)
goto out_fail;
- MSDOS_I(fat_inode)->i_pos = 0;
+ fat_dummy_inode_init(fat_inode);
sbi->fat_inode = fat_inode;

fsinfo_inode = new_inode(sb);
if (!fsinfo_inode)
goto out_fail;
+ fat_dummy_inode_init(fsinfo_inode);
fsinfo_inode->i_ino = MSDOS_FSINFO_INO;
sbi->fsinfo_inode = fsinfo_inode;
insert_inode_hash(fsinfo_inode);

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