On Thu 2018-09-20 12:30:56, Steven Rostedt wrote:
> On Fri, 21 Sep 2018 00:16:50 +0800
> He Zhe <zhe...@windriver.com> wrote:
>
> > On 2018年09月19日 10:43, Steven Rostedt wrote:
> > > On Wed, 19 Sep 2018 11:39:32 +0900
> > > Sergey Senozhatsky <sergey.senozhatsky.w...@gmail.com> wrote:
> > >
> > >> On (09/19/18 10:27), He Zhe wrote:
> > >>> On 2018年09月19日 09:50, Sergey Senozhatsky wrote:
> > >>>> On (09/19/18 01:17), zhe...@windriver.com wrote:
> > >>>>> @@ -1048,7 +1048,14 @@ static void __init log_buf_len_update(unsigned
> > >>>>> size)
> > >>>>> /* save requested log_buf_len since it's too early to process it */
> > >>>>> static int __init log_buf_len_setup(char *str)
> > >>>>> {
> > >>>>> - unsigned size = memparse(str, &str);
> > >>>>> + unsigned size;
> > >>>> unsigned int size;
> > >>> This is in v1 but then Steven suggested that it should be split out
> > >>> and only keep the pure fix part here.
> > >> Ah, I see.
> > >>
> > >> Hmm... memparse() returns u64 value. A user *probably* can ask the kernel
> > >> to allocate log_buf larger than 'unsigned int'.
> > >>
> > >> So may be I'd do two fixes here:
> > >>
> > >> First - switch to u64 size.
> > >> Second - check for NULL str.
> > >>
> > >>
> > >> Steven, Petr, what do you think?
> > >>
> > > I think I would switch it around. Check for NULL first, and then switch
> > > to u64. It was always an int, do we need to backport converting it to
> > > u64 to stable? The NULL check is a definite, the overflow of int
> > > shouldn't crash anything.
> >
>
> Hi Zhe,
>
> > To switch to u64, several variables need to be adjusted to new type to
> > aligned
> > with new_log_buf_len. And currently new_log_buf_len is passed to
> > memblock_virt_alloc(phys_addr_t, phys_addr_t). So we can't simply define
> > new_log_buf_len as u64. We need to define it as phys_addr_t tomake it work
> > well for both 32bit and 64bit arches, since a 32-bit architecture can set
> > ARCH_PHYS_ADDR_T_64BIT if it needs a 64-bit phys_addr_t.
>
> The above explanation verifies more that the NULL pointer check needs
> to be first, and that the change in size should not be backported to
> stable because it has a high risk to doing the change as compared to it
> being a problem for older kernels.
I agree that the NULL check should go first.
I would personally keep the size as unsigned int. IMHO, a support
for a log buffer bigger than 4GB is not worth the complexity.
Best Regards,
Petr
