Messages in this thread | | | Date | Wed, 22 May 2019 19:24:49 +0800 | From | Gen Zhang <> | Subject | Re: [PATCH] tty_io: Fix a missing-check bug in drivers/tty/tty_io.c |
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On Wed, May 22, 2019 at 01:19:49PM +0200, Johan Hovold wrote: > On Wed, May 22, 2019 at 07:13:54PM +0800, Gen Zhang wrote: > > On Wed, May 22, 2019 at 12:29:00PM +0200, Johan Hovold wrote: > > > Where do you see that the kernel is dereferencing tty->dev without > > > checking for NULL first? If you can find that, then that would indeed be > > > a bug that needs fixing. > > Thanks for your reply, Johan! > > I examined the code but failed to find this situation. > > Ok, so your claim in the commit message was incorrect: > > And tty->dev is dereferenced in the following codes. > > > Anyway, checking return value of tty_get_device() is theoritically > > right. But tty->dev is never dereferenced, so checking is not needed. > > No, sorry, it's not even theoretically correct. Our current code depends > on tty->dev sometimes being NULL. Your patch would specifically break > pseudo terminals. Thanks for your comments. I have to be very proficient in this module to know this. Of course I am not. Anyway, appreciate your replies, Johan. Thanks Gen > > > However, what if in later kernels tty->dev is dereferenced by some > > codes? Is it better to apply this check for this reason? > > So for the above reason, no. > > Johan
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