Messages in this thread | | | Date | Thu, 4 Aug 2022 11:22:26 +0200 | Subject | Re: [PATCH] tty: vt: selection: Add check for valid tiocl_selection values | From | Jiri Slaby <> |
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On 04. 08. 22, 10:44, Helge Deller wrote: > On 8/4/22 09:15, Helge Deller wrote: >> Hello Jiri, >> >> Thanks for looking into this patch! >> >> On 8/4/22 07:47, Jiri Slaby wrote: >>> On 30. 07. 22, 20:49, Helge Deller wrote: >>>> The line and column numbers for the selection need to start at 1. >>>> Add the checks to prevent invalid input. >>>> >>>> Signed-off-by: Helge Deller <deller@gmx.de> >>>> Reported-by: syzbot+14b0e8f3fd1612e35350@syzkaller.appspotmail.com >>>> >>>> diff --git a/drivers/tty/vt/selection.c b/drivers/tty/vt/selection.c >>>> index f7755e73696e..58692a9b4097 100644 >>>> --- a/drivers/tty/vt/selection.c >>>> +++ b/drivers/tty/vt/selection.c >>>> @@ -326,6 +326,9 @@ static int vc_selection(struct vc_data *vc, struct tiocl_selection *v, >>>> return 0; >>>> } >>>> >>>> + if (!v->xs || !v->ys || !v->xe || !v->ye) >>>> + return -EINVAL; >>> >>> Hmm, I'm not sure about this. It potentially breaks userspace (by >>> returning EINVAL now). >> >> Right. >> According to the code below, my interpretation is that all xs/ys/xe/ye values >> should be > 0. But of course I might be wrong on this, as I didn't find any >> documentation for TIOCL_SETSEL. >> >> And if userspace tries to set an invalid selection (e.g. by selecting row 0), >> my patch now returns -EINVAL, while it returned success before. >> >>> And the code below should handle this just fine, right: >>>> v->xs = min_t(u16, v->xs - 1, vc->vc_cols - 1); >>>> v->ys = min_t(u16, v->ys - 1, vc->vc_rows - 1); >>>> v->xe = min_t(u16, v->xe - 1, vc->vc_cols - 1); >> >> It "handles it fine" in the sense that it can cope with the >> input and will not crash. >> But it returns (maybe?) unexpected results... > > After some more thinking maybe you are right. > In case a user provided invalid values in the past, simply an unexpected > selection was set, but nothing broke. > Since the patch doesn't fix any critical issue, we could just drop this patch > and leave it as is.
We can still do a trial and revert it if something breaks... It's just that _noone_ knows with all this undocumented stuff ;).
But in fact, 0 currently means full row/column. Isn't it on purpose?
Today, we are out of luck, codesearch.debian.net gives no clue about users: https://codesearch.debian.net/search?q=%5CbTIOCL_SETSEL%5Cb&literal=0
thanks, -- js suse labs
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