Re: [GIT PULL] TTY/Serial driver fixes for 4.11-rc4

[Linus Torvalds]

On Thu, Apr 13, 2017 at 3:50 AM, Vegard Nossum <vegard.nossum@xxxxxxxxx> wrote:
>
> I've bisected a syzkaller crash down to this commit
> (5362544bebe85071188dd9e479b5a5040841c895). The crash is:
>
> [   25.137552] BUG: unable to handle kernel paging request at 0000000000002280
> [   25.137579] IP: mutex_lock_interruptible+0xb/0x30

It would seem to be the

                if (mutex_lock_interruptible(&ldata->atomic_read_lock))

call in n_tty_read(), the offset is about right for a NULL 'ldata'
pointer (it's a big structure, it has a couple of character buffers of
size N_TTY_BUF_SIZE).

I don't see the obvious fix, so I suspect at this point we should just
revert, as that commit seems to introduce worse problems that it is
supposed to fix. Greg?

              Linus