Date: Thu, 22 Apr 2010 17:45:38 -0700 From: Garrett Cooper <yanefbsd@gmail.com> To: Matthew Fleming <matthew.fleming@isilon.com> Cc: FreeBSD-Hackers <freebsd-hackers@freebsd.org> Subject: Re: Error checking in ioctl(2)? Message-ID: <u2o7d6fde3d1004221745o32173f04hdf77c080979026c8@mail.gmail.com> In-Reply-To: <06D5F9F6F655AD4C92E28B662F7F853E039E33A7@seaxch09.desktop.isilon.com> References: <w2v7d6fde3d1004221627jff97746bkcb8cd3ca5e5a7492@mail.gmail.com> <06D5F9F6F655AD4C92E28B662F7F853E039E33A7@seaxch09.desktop.isilon.com>
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On Thu, Apr 22, 2010 at 4:36 PM, Matthew Fleming
<matthew.fleming@isilon.com> wrote:
>> Hi hackers,
>> =A0 =A0 I realize that this isn't 100% userland code, so the checks shou=
ld
>> be minimalized, but when looking at the ioctl(2) syscall code (at
>> least I think it is... there's another dupe hanging around in
>> sys/dev/hptmv/ioctl.c), I had some questions related to the error
>> handling not being done in the code:
>>
>> =A0 =A0 =A0 =A0 if (size > 0) {
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (com & IOC_VOID) {
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* Integer argument. */
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 arg =3D (intptr_t)uap->d=
ata;
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 data =3D (void *)&arg;
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 size =3D 0;
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 } else
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 data =3D malloc((u_long)=
size, M_IOCTLOPS,
>> M_WAITOK); /* XXX: can fail -- do we care? */
>
> malloc(9) with M_WAITOK cannot return NULL. =A0So the rest of your XXX
> comments are not at issue.
>
> Also, free(9) is documented to do the right thing when asked to
> free(NULL).
>
> copyin/copyout are really just bcopy but unlike most kernel code they
> are allowed to take a page fault. =A0They deal with this by setting a
> function pointer in PCB_ONFAULT, which is used in trap() to set a return
> instruction pointer.
Matt,
Awesome. I can see I need to do a bit more reading in malloc(3) :)...
Thanks for the info!
-Garrett
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