Messages in this thread | | | Date | Wed, 16 Jan 2019 12:15:07 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v15 6/6] x86/boot/KASLR: Limit KASLR to extracting kernel in immovable memory |
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On Mon, Jan 07, 2019 at 11:22:43AM +0800, Chao Fan wrote: > KASLR may randomly choose some positions which are located in movable > memory regions. It will break memory hotplug feature and make the > movable memory chosen by KASLR can't be removed. > > The solution is to limit KASLR to choose memory regions in immovable > node according to SRAT tables. > When CONFIG_EARLY_SRAT_PARSE is enabled, walk through SRAT to get the > information of immovable memory so that KASLR knows where should be > chosen for randomization. > > Rename process_mem_region() as __process_mem_region() and name new > function as process_mem_region().
The commit message doesn't need to contain *what* you're doing in the patch.
> > Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com> > --- > arch/x86/boot/compressed/kaslr.c | 79 +++++++++++++++++++++++++++----- > 1 file changed, 68 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c > index b251572e77af..7dbec6910203 100644 > --- a/arch/x86/boot/compressed/kaslr.c > +++ b/arch/x86/boot/compressed/kaslr.c > @@ -97,6 +97,15 @@ static bool memmap_too_large; > /* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */ > static unsigned long long mem_limit = ULLONG_MAX; > > +#ifdef CONFIG_EARLY_SRAT_PARSE > +/* > + * Information of immovable memory regions. > + * Max amount of memory regions is MAX_NUMNODES*2, so need such array > + * to place immovable memory regions if all of the memory is immovable. > + */
Why is that comment repeated here?
> +extern struct mem_vector immovable_mem[MAX_NUMNODES*2]; > +#endif > + > > enum mem_avoid_index { > MEM_AVOID_ZO_RANGE = 0, > @@ -413,6 +422,9 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size, > /* Mark the memmap regions we need to avoid */ > handle_mem_options(); > > + /* Mark the immovable regions we need to choose */ > + get_immovable_mem();
get != mark.
Which should tell you that the function name needs changing.
Also, this function is void and it could very well return num_immovable_mem and num_immovable_mem can be a static variable in kaslr.c instead of sloppily adding yet another global one.
> + > #ifdef CONFIG_X86_VERBOSE_BOOTUP > /* Make sure video RAM can be used. */ > add_identity_map(0, PMD_SIZE); > @@ -568,9 +580,9 @@ static unsigned long slots_fetch_random(void) > return 0; > } > > -static void process_mem_region(struct mem_vector *entry, > - unsigned long minimum, > - unsigned long image_size) > +static void __process_mem_region(struct mem_vector *entry, > + unsigned long minimum, > + unsigned long image_size) > { > struct mem_vector region, overlap; > unsigned long start_orig, end; > @@ -646,6 +658,57 @@ static void process_mem_region(struct mem_vector *entry, > } > } > > +static bool process_mem_region(struct mem_vector *region, > + unsigned long long minimum, > + unsigned long long image_size) > +{ > + int i; > + /* > + * If no immovable memory found, or MEMORY_HOTREMOVE disabled, > + * walk all the regions, so use region directly. > + */ > + if (!num_immovable_mem) { > + __process_mem_region(region, minimum, image_size); > + > + if (slot_area_index == MAX_SLOT_AREA) { > + debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n"); > + return 1; > + } > + return 0; > + } > + > +#ifdef CONFIG_EARLY_SRAT_PARSE > + /* > + * If immovable memory found, filter the intersection between > + * immovable memory and region to __process_mem_region(). > + * Otherwise, go on old code. > + */ > + for (i = 0; i < num_immovable_mem; i++) { > + unsigned long long start, end, entry_end, region_end; > + struct mem_vector entry; > + > + if (!mem_overlaps(region, &immovable_mem[i])) > + continue; > + > + start = immovable_mem[i].start; > + end = start + immovable_mem[i].size; > + region_end = region->start + region->size; > + > + entry.start = clamp(region->start, start, end); > + entry_end = clamp(region_end, start, end); > + entry.size = entry_end - entry.start; > + > + __process_mem_region(&entry, minimum, image_size); > + > + if (slot_area_index == MAX_SLOT_AREA) { > + debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
Change this error message a bit to differ from the above for easier debugging.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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