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.
>
> What do you think?
Sounds good to me.
What do others think?
-- Steve
