Messages in this thread | | | Date | Wed, 19 Apr 2017 08:59:06 +0800 | From | Baoquan He <> | Subject | Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option |
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On 04/19/17 at 08:50am, Baoquan He wrote: > On 04/18/17 at 01:36pm, Kees Cook wrote: > > On Mon, Apr 17, 2017 at 6:34 AM, Baoquan He <bhe@redhat.com> wrote: > > > @@ -432,7 +455,8 @@ static void process_e820_entry(struct e820entry *entry, > > > { > > > struct mem_vector region, overlap; > > > struct slot_area slot_area; > > > - unsigned long start_orig; > > > + unsigned long start_orig, end; > > > + struct e820entry cur_entry; > > > > > > /* Skip non-RAM entries. */ > > > if (entry->type != E820_RAM) > > > @@ -446,8 +470,15 @@ static void process_e820_entry(struct e820entry *entry, > > > if (entry->addr + entry->size < minimum) > > > return; > > > > > > - region.start = entry->addr; > > > - region.size = entry->size; > > > + /* Ignore entries above memory limit */ > > > + end = min(entry->size + entry->addr - 1, mem_limit); > > > + if (entry->addr >= end) > > > + return; > > > + cur_entry.addr = entry->addr; > > > + cur_entry.size = end - entry->addr + 1; > > > + > > > + region.start = cur_entry.addr; > > > + region.size = cur_entry.size; > > > > I find the manipulation of entry->addr +/- 1 confusing; it should just > > be mem_limit that is adjusted: > > > > end = min(entry->size + entry->addr, mem_limit + 1); > > Oh, it should be like that. E.g if specify mem=4096M, it means available ^not > memory region are 0~4096M-1, or [0, 4096M). Here mem_limit = 4096M. > Adding 1 could make it wrong. > > > > > And maybe to avoid mem_limit being giant by default, maybe have "0" be special? > > > > cur_entry.addr = entry->addr; > > if (mem_limit) { > > unsigned long end = min(entry->size + entry->addr, mem_limit + 1); > > if (entry->addr > end) > > return; > > cur_entry.size = end - entry->addr; > > } else { > > cur_entry.size = entry->size; > > } > > > > or something... and maybe move the whole thing earlier so other tests > > that examine entry->size are checked with the new adjusted value. > > Sorry, forget replying to this comment. I am fine with moving it > earlier. In fact I put it here because there are many non-RAM e820 > entries below 4G, like ACPI, for them we even don't need check limit > by the help of below check filtering. Maybe move it after below check? > > /* Skip non-RAM entries. */ > if (entry->type != E820_RAM) > return; > > > > > -Kees > > > > > > > > /* Give up if slot area array is full. */ > > > while (slot_area_index < MAX_SLOT_AREA) { > > > @@ -461,7 +492,7 @@ static void process_e820_entry(struct e820entry *entry, > > > region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN); > > > > > > /* Did we raise the address above this e820 region? */ > > > - if (region.start > entry->addr + entry->size) > > > + if (region.start > cur_entry.addr + cur_entry.size) > > > return; > > > > > > /* Reduce size by any delta from the original address. */ > > > -- > > > 2.5.5 > > > > > > > > > > > -- > > Kees Cook > > Pixel Security
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