Following process makes i_disksize exceed i_size:
generic_perform_write
copied = iov_iter_copy_from_user_atomic(len) // copied < len
ext4_da_write_end
| ext4_update_i_disksize
| new_i_size = pos + copied;
| WRITE_ONCE(EXT4_I(inode)->i_disksize, newsize) // update i_disksize
| generic_write_end
| copied = block_write_end(copied, len) // copied = 0
| if (unlikely(copied < len))
| if (!PageUptodate(page))
| copied = 0;
| if (pos + copied > inode->i_size) // return false
if (unlikely(copied == 0))
goto again;
if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
status = -EFAULT;
break;
}
We get i_disksize greater than i_size here, which could trigger WARNING
check 'i_size_read(inode) < EXT4_I(inode)->i_disksize' while doing dio:
ext4_dio_write_iter
iomap_dio_rw
__iomap_dio_rw // return err, length is not aligned to 512
ext4_handle_inode_extension
WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize) // Oops
WARNING: CPU: 2 PID: 2609 at fs/ext4/file.c:319
CPU: 2 PID: 2609 Comm: aa Not tainted 6.3.0-rc2
RIP: 0010:ext4_file_write_iter+0xbc7
Call Trace:
vfs_write+0x3b1
ksys_write+0x77
do_syscall_64+0x39
Fix it by updating 'copied' value before updating i_disksize just like
ext4_write_inline_data_end() does.
Fetch a reproducer in [Link].
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217209
Fixes: 64769240bd07 ("ext4: Add delayed allocation support in data=writeback mode")
Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
---
v1->v2: Check and update 'copied' value before updating i_disksize rather
than opencoding generic_write_end().
fs/ext4/inode.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index bf0b7dea4900..41ba1c432844 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3148,6 +3148,9 @@ static int ext4_da_write_end(struct file *file,
ext4_has_inline_data(inode))
return ext4_write_inline_data_end(inode, pos, len, copied, page);
+ if (unlikely(copied < len) && !PageUptodate(page))
+ copied = 0;
+
start = pos & (PAGE_SIZE - 1);
end = start + copied - 1;
--
2.31.1
