Commit d0b040f5 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
Browse files

ext4: fix overflow in ext4_iomap_alloc() 



A code in iomap alloc may overflow block number when converting it to
byte offset. Luckily this is mostly harmless as we will just use more
expensive method of writing using unwritten extents even though we are
writing beyond i_size.

Cc: stable@kernel.org
Fixes: 378f32ba ("ext4: introduce direct I/O write using iomap infrastructure")
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210412102333.2676-4-jack@suse.cz


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 614124be

fs/ext4/inode.c

+1 −1
Original line number Diff line number Diff line
@@ -3418,7 +3418,7 @@ static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map, 
	 * i_disksize out to i_size. This could be beyond where direct I/O is

	 * happening and thus expose allocated blocks to direct I/O reads.

	 */

	else if ((map->m_lblk * (1 << blkbits)) >= i_size_read(inode))

	else if (((loff_t)map->m_lblk << blkbits) >= i_size_read(inode))

		m_flags = EXT4_GET_BLOCKS_CREATE;

	else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))

		m_flags = EXT4_GET_BLOCKS_IO_CREATE_EXT;