Messages in this thread Patch in this message | | | From | Baoquan He <> | Subject | [PATCH v3 08/19] x86, kaslr: Consolidate mem_avoid array filling | Date | Sat, 5 Mar 2016 00:25:06 +0800 |
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From: Yinghai Lu <yinghai@kernel.org>
We are going to support kaslr with 64bit above 4G, and new random output could be anywhere. Array mem_avoid is used for kaslr to search new output address. Current code only track range that is after output+output_size. So we need to track all ranges instead of just after output+output_size.
Current code has first entry which is extra bytes before input+input_size, and it is according to output_size. Other entries are for initrd, cmdline, and heap/stack for ZO running.
At first, let's check the first entry that should be in the mem_avoid array. Now ZO sit end of the buffer always, we can find out where is text and data/bss etc of ZO.
Since init_size >= run_size, and input+input_len >= output+output_len, here make several assumptions for better presentation by graph: - init_size > run_size - input+input_len > output+output_len - run_size > output_len
0 output input input+input_len output+init_size | | | | | |-----|-------------------|--------|------------------|----|------------|----------| | | | output+init_size-ZO_INIT_SIZE output+output_len output+run_size
[output, output+init_size) is the for decompressing buffer for compressed kernel.
[output, output+run_size) is for VO run size. [output, output+output_len) is (VO (vmlinux after objcopy) plus relocs)
[output+init_size-ZO_INIT_SIZE, output+init_size) is copied ZO. [input, input+input_len) is copied compressed (VO (vmlinux after objcopy) plus relocs), not the ZO.
[input+input_len, output+init_size) is [_text, _end) for ZO. that could be first range in mem_avoid. Now the new first entry already includes heap and stack for ZO running. So no need to put them separately into mem_avoid array.
Also [input, input+input_size) need be put in mem_avoid array. It is adjacent to new first entry, so merge them.
At last we need to put boot_params into the mem_avoid too. As with 64bit bootloader could put it anywhere.
After these changes, we have all ranges which need be avoided in mem_avoid array.
Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Yinghai Lu <yinghai@kernel.org> --- v2->v3: Adjust the patch log.
arch/x86/boot/compressed/aslr.c | 29 +++++++++++++---------------- 1 file changed, 13 insertions(+), 16 deletions(-)
diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c index 622aa88..b93be03 100644 --- a/arch/x86/boot/compressed/aslr.c +++ b/arch/x86/boot/compressed/aslr.c @@ -109,7 +109,7 @@ struct mem_vector { unsigned long size; }; -#define MEM_AVOID_MAX 5 +#define MEM_AVOID_MAX 4 static struct mem_vector mem_avoid[MEM_AVOID_MAX]; static bool mem_contains(struct mem_vector *region, struct mem_vector *item) @@ -135,21 +135,22 @@ static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two) } static void mem_avoid_init(unsigned long input, unsigned long input_size, - unsigned long output, unsigned long output_size) + unsigned long output) { + unsigned long init_size = real_mode->hdr.init_size; u64 initrd_start, initrd_size; u64 cmd_line, cmd_line_size; - unsigned long unsafe, unsafe_len; char *ptr; /* * Avoid the region that is unsafe to overlap during - * decompression (see calculations at top of misc.c). + * decompression. + * As we already move ZO (arch/x86/boot/compressed/vmlinux) + * to the end of buffer, [input+input_size, output+init_size) + * has [_text, _end) for ZO. */ - unsafe_len = (output_size >> 12) + 32768 + 18; - unsafe = (unsigned long)input + input_size - unsafe_len; - mem_avoid[0].start = unsafe; - mem_avoid[0].size = unsafe_len; + mem_avoid[0].start = input; + mem_avoid[0].size = (output + init_size) - input; /* Avoid initrd. */ initrd_start = (u64)real_mode->ext_ramdisk_image << 32; @@ -169,13 +170,9 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size, mem_avoid[2].start = cmd_line; mem_avoid[2].size = cmd_line_size; - /* Avoid heap memory. */ - mem_avoid[3].start = (unsigned long)free_mem_ptr; - mem_avoid[3].size = BOOT_HEAP_SIZE; - - /* Avoid stack memory. */ - mem_avoid[4].start = (unsigned long)free_mem_end_ptr; - mem_avoid[4].size = BOOT_STACK_SIZE; + /* Avoid params */ + mem_avoid[3].start = (unsigned long)real_mode; + mem_avoid[3].size = sizeof(*real_mode); } /* Does this memory vector overlap a known avoided area? */ @@ -319,7 +316,7 @@ unsigned char *choose_kernel_location(unsigned char *input, /* Record the various known unsafe memory ranges. */ mem_avoid_init((unsigned long)input, input_size, - (unsigned long)output, output_size); + (unsigned long)output); /* Walk e820 and find a random address. */ random = find_random_addr(choice, output_size); -- 2.5.0
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