Re: [PATCH v2] ubifs: Fix read out-of-bounds in ubifs_jnl_write_inode()

[Zhihao Cheng]

在 2020/12/24 7:07, Richard Weinberger 写道:

> > Reproducer:
> > 0. config KASAN && apply print.patch
> > 1. mount ubifs on /root/temp
> > 2. run test.sh
>
> What does test.sh do?
Go to Link: https://bugzilla.kernel.org/show_bug.cgi?id=210865.
test.sh creates a very long path file test_file, and then create a 
symbol link link_file for test_file, so ubifs inode for link_file will 
be assigned a big value for ui->data_len.
When we change atime for link_file, ubifs_jnl_write_inode will be 
executed by wb_writeback. By this way, write_len could be not aligned 
with 8 bytes.
> > 3. cd /root/temp && ls // change atime for link_file
> > 4. wait 1~2 minutes
> >
> > In order to solve the read oob problem in ubifs_wbuf_write_nolock, just align
> > the write_len to
> > 8 bytes when alloc the memory. So that this patch will not affect the use of
> > write_len in other
> > functions, such as ubifs_jnl_write_inode->make_reservation and
> > ubifs_jnl_write_inode->ubifs_node_calc_hash.
>
> I gave this a second thought and I'm not so sure anymore what exactly is going on.
> The problem is real, I fully agree with you but I need to dig deeper into
> the journal and wbuf code to double check that we really fix the right thing
> and not just paper other something.
>
> Thanks,
> //richard
> .