From 157e757a305b5191133fe7ffa60f55a895049fcf Mon Sep 17 00:00:00 2001 From: Eryu Guan Date: Thu, 22 Mar 2018 11:41:25 -0400 Subject: [PATCH] ext4: protect i_disksize update by i_data_sem in direct write path commit 73fdad00b208b139cf43f3163fbc0f67e4c6047c upstream. 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 Suggested-by: Jan Kara Signed-off-by: Eryu Guan Signed-off-by: Theodore Ts'o [bwh: Backported to 3.16: The relevant code is in ext4_ind_direct_IO()] Signed-off-by: Ben Hutchings --- fs/ext4/indirect.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c index b07a221c3138..b8861b4edc2a 100644 --- a/fs/ext4/indirect.c +++ b/fs/ext4/indirect.c @@ -651,7 +651,6 @@ ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb, { struct file *file = iocb->ki_filp; struct inode *inode = file->f_mapping->host; - struct ext4_inode_info *ei = EXT4_I(inode); handle_t *handle; ssize_t ret; int orphan = 0; @@ -674,7 +673,7 @@ ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb, goto out; } orphan = 1; - ei->i_disksize = inode->i_size; + ext4_update_i_disksize(inode, inode->i_size); ext4_journal_stop(handle); } } @@ -739,7 +738,7 @@ locked: 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'