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 <[email protected]>
* Andy Shevchenko <[email protected]>
* Johan Hovold <[email protected]>
Signed-off-by: Ajay Garg <[email protected]>
---
There were discussions previously, and the current patch is the
result.
v1 :
https://lore.kernel.org/linux-serial/[email protected]/T/#t
v2 :
https://lore.kernel.org/linux-serial/CAHP4M8Vdj4Eb8q773BeHvsW9n6t=3n1WznuXAR4fZCNi1J6rOg@mail.gmail.com/T/#m18f45676feaba6b1f01ddd5fe607997b190ef4b9
v3 :
https://lore.kernel.org/linux-serial/[email protected]/T/#u
v4 :
https://lore.kernel.org/linux-serial/[email protected]/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
On Mon, Nov 08, 2021 at 07:24:59PM +0530, Ajay Garg wrote:
> 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 <[email protected]> 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.
You are listing two different things being done in this single commit.
It should be 2 different patches.
I would recommend getting more comfortable with Linux kernel development
by working in the drivers/staging/ portion of the kernel first. And not
in the "core" kernel like tty/serial or other well-entrenched
subsystems. That way you can learn the proper processes and workflows
better in an area of the kernel that is specifically designed just for
that, and not end up bothering the time of other kernel developers for
basic process issues like your recent patches have shown.
thanks,
greg k-h