From e251f9bca99c0f219eff9c76034476c2b17d3dba Mon Sep 17 00:00:00 2001 From: Maxim Patlasov Date: Thu, 20 Feb 2014 16:58:05 -0500 Subject: [PATCH] ext4: avoid exposure of stale data in ext4_punch_hole() While handling punch-hole fallocate, it's useless to truncate page cache before removing the range from extent tree (or block map in indirect case) because page cache can be re-populated (by read-ahead or read(2) or mmap-ed read) immediately after truncating page cache, but before updating extent tree (or block map). In that case the user will see stale data even after fallocate is completed. Until the problem of data corruption resulting from pages backed by already freed blocks is fully resolved, the simple thing we can do now is to add another truncation of pagecache after punch hole is done. Signed-off-by: Maxim Patlasov Signed-off-by: "Theodore Ts'o" Reviewed-by: Jan Kara --- fs/ext4/inode.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 113458c9d08b..5324a38d848d 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3614,6 +3614,12 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length) up_write(&EXT4_I(inode)->i_data_sem); if (IS_SYNC(inode)) ext4_handle_sync(handle); + + /* Now release the pages again to reduce race window */ + if (last_block_offset > first_block_offset) + truncate_pagecache_range(inode, first_block_offset, + last_block_offset); + inode->i_mtime = inode->i_ctime = ext4_current_time(inode); ext4_mark_inode_dirty(handle, inode); out_stop: -- 2.20.1