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ext4: protect i_disksize update by i_data_sem in direct write path

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i_disksize update should be protected by i_data_sem, by either taking
the lock explicitly or by using ext4_update_i_disksize() helper. But the
i_disksize updates in ext4_direct_IO_write() are not protected at all,
which may be racing with i_disksize updates in writeback path in
delalloc buffer write path.

This is found by code inspection, and I didn't hit any i_disksize
corruption due to this bug. Thanks to Jan Kara for catching this bug and
suggesting the fix!

Reported-by: Jan Kara <jack@suse.cz>
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
This commit is contained in:
Eryu Guan 2018-03-22 11:41:25 -04:00 committed by Theodore Ts'o
parent 044e6e3d74
commit 73fdad00b2
1 changed files with 2 additions and 3 deletions
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5
fs/ext4/inode.c
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@ -3658,7 +3658,6 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
struct ext4_inode_info *ei = EXT4_I(inode);
ssize_t ret;
loff_t offset = iocb->ki_pos;
size_t count = iov_iter_count(iter);
@ -3682,7 +3681,7 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
goto out;
}
orphan = 1;
ei->i_disksize = inode->i_size;
ext4_update_i_disksize(inode, inode->i_size);
ext4_journal_stop(handle);
}
@ -3790,7 +3789,7 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
if (ret > 0) {
loff_t end = offset + ret;
if (end > inode->i_size) {
ei->i_disksize = end;
ext4_update_i_disksize(inode, end);
i_size_write(inode, end);
/*
* We're going to return a positive `ret'