Re: [PATCH v5] vt: keyboard: suppress warnings in vt_do_kdgkb_ioctl

[Ajay Garg]

Hmm, I am afraid I don't understand. The patch changes only 5 lines.
Could someone help me navigate what to "fix"?


Thanks and Regards,
Ajay

On Mon, Nov 8, 2021 at 7:22 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Mon, Nov 08, 2021 at 07:19:01PM +0530, Ajay Garg wrote:
> > smatch-kchecker gives the following warnings when run on keyboard.c :
> >
> > vt_do_kdgkb_ioctl() error: uninitialized symbol 'kbs'.
> > vt_do_kdgkb_ioctl() error: uninitialized symbol 'ret'.
> >
> > i)
> > The 'kbs" warning was introduced by "07edff926520" :
> > ("vt: keyboard, reorder user buffer handling in vt_do_kdgkb_ioctl")
> >
> > *
> > prior 07edff926520, the scope of kbs (allocation/deallocation) was
> > external to switch-cases.
> >
> > *
> > post 07edff926520, kbs is allocated internally for each case, however the
> > deallocation remains external.
> >
> > Thus, as the "fix", the scope of kbs deallocation is now made internal
> > to each switch case.
> >
> > ii)
> > The 'ret' warning is the result of "4e1404a5cd04" :
> > ("vt: keyboard, extract and simplify vt_kdskbsent")
> >
> > where the "ret = 0" (right at the end) was accidentally removed.
> >
> > Bringing back the above in a slightly different way, by initializing ret
> > to 0 at the start.
> >
> > Many thanks to the following for review of previous versions :
> >
> >       * Pavel Skripkin <paskripkin@xxxxxxxxx>
> >       * Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> >       * Johan Hovold <johan@xxxxxxxxxx>
> >
> > Signed-off-by: Ajay Garg <ajaygargnsit@xxxxxxxxx>
> > ---
> >
> > There were discussions previously, and the current patch is the
> > result.
> >
> > v1 :
> > https://lore.kernel.org/linux-serial/YYZN30qfaKMskVwE@xxxxxxxxx/T/#t
> >
> > v2 :
> > https://lore.kernel.org/linux-serial/CAHP4M8Vdj4Eb8q773BeHvsW9n6t=3n1WznuXAR4fZCNi1J6rOg@xxxxxxxxxxxxxx/T/#m18f45676feaba6b1f01ddd5fe607997b190ef4b9
> >
> > v3 :
> > https://lore.kernel.org/linux-serial/20211106220315.392842-1-ajaygargnsit@xxxxxxxxx/T/#u
> >
> > v4 :
> > https://lore.kernel.org/linux-serial/YYjw2mRIhy1SoIb+@xxxxxxxxxxxxxxxxxxxx/T/#mf25ca00a93e278bbb8f0382a4f7752dc35f4aa8b
> >
> > Changes in v2 :
> >
> >         * Changes as required by scripts/checkpatch.pl
> >
> >         * Checking whether kbs is not NULL before kfree is not required,
> >           as kfree(NULL) is safe. So, dropped the check.
> >
> > Changes in v3 :
> >
> >         * Using default-switch case, and setting the variables
> >           when there is no matching cmd.
> >
> > Changes in v4 :
> >
> >         * Removed braces for the default switch-case.
> >
> > Changes in v5 :
> >
> >         * Incorporating changes as suggested by Johan Hovold
> >         (please see v4 link).
> >
> >  drivers/tty/vt/keyboard.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
> > index c7fbbcdcc346..ea19671d5d0c 100644
> > --- a/drivers/tty/vt/keyboard.c
> > +++ b/drivers/tty/vt/keyboard.c
> > @@ -2050,7 +2050,7 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
> >       unsigned char kb_func;
> >       unsigned long flags;
> >       char *kbs;
> > -     int ret;
> > +     int ret = 0;
> >
> >       if (get_user(kb_func, &user_kdgkb->kb_func))
> >               return -EFAULT;
> > @@ -2073,6 +2073,7 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
> >               ret = copy_to_user(user_kdgkb->kb_string, kbs, len + 1) ?
> >                       -EFAULT : 0;
> >
> > +             kfree(kbs);
> >               break;
> >       }
> >       case KDSKBSENT:
> > @@ -2088,11 +2089,11 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
> >               kbs = vt_kdskbsent(kbs, kb_func);
> >               spin_unlock_irqrestore(&func_buf_lock, flags);
> >
> > +             kfree(kbs);
> >               ret = 0;
> >               break;
> >       }
> >
> > -     kfree(kbs);
> >
> >       return ret;
> >  }
> > --
> > 2.30.2
> >
>
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>
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