Hi all,
On 8/19/19 9:16 AM, tip-bot for Kirill A. Shutemov wrote:
[..]
>
> diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
> index 5f2d03067ae5..2faddeb0398a 100644
> --- a/arch/x86/boot/compressed/pgtable_64.c
> +++ b/arch/x86/boot/compressed/pgtable_64.c
> @@ -72,6 +72,8 @@ static unsigned long find_trampoline_placement(void)
>
> /* Find the first usable memory region under bios_start. */
> for (i = boot_params->e820_entries - 1; i >= 0; i--) {
> + unsigned long new;
> +
> entry = &boot_params->e820_table[i];
>
> /* Skip all entries above bios_start. */
> @@ -84,15 +86,20 @@ static unsigned long find_trampoline_placement(void)
>
> /* Adjust bios_start to the end of the entry if needed. */
> if (bios_start > entry->addr + entry->size)
Notice that if this condition happens to be false, we end up with an
uninitialized variable *new*.
What would be the right value to assign to *new* at declaration under
this condition?
> - bios_start = entry->addr + entry->size;
> + new = entry->addr + entry->size;
>
> /* Keep bios_start page-aligned. */
> - bios_start = round_down(bios_start, PAGE_SIZE);
> + new = round_down(new, PAGE_SIZE);
>
> /* Skip the entry if it's too small. */
> - if (bios_start - TRAMPOLINE_32BIT_SIZE < entry->addr)
> + if (new - TRAMPOLINE_32BIT_SIZE < entry->addr)
> continue;
>
> + /* Protect against underflow. */
> + if (new - TRAMPOLINE_32BIT_SIZE > bios_start)
> + break;
> +
> + bios_start = new;
> break;
> }
>
>
--
Gustavo
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