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authorYinghai Lu <yinghai@kernel.org>2015-02-19 20:18:03 -0800
committerMatt Fleming <matt.fleming@intel.com>2015-02-24 18:46:03 +0000
commit7ed620bb343f434f8a85f830020c04988df2a140 (patch)
tree174badf33371a6d7c55347508e52196930900bb2
parentce204e9a4bd82e9e6e7479bca8057e45aaac5c42 (diff)
efi/libstub: Fix boundary checking in efi_high_alloc()
While adding support loading kernel and initrd above 4G to grub2 in legacy mode, I was referring to efi_high_alloc(). That will allocate buffer for kernel and then initrd, and initrd will use kernel buffer start as limit. During testing found two buffers will be overlapped when initrd size is very big like 400M. It turns out efi_high_alloc() boundary checking is not right. end - size will be the new start, and should not compare new start with max, we need to make sure end is smaller than max. [ Basically, with the current efi_high_alloc() code it's possible to allocate memory above 'max', because efi_high_alloc() doesn't check that the tail of the allocation is below 'max'. If you have an EFI memory map with a single entry that looks like so, [0xc0000000-0xc0004000] And want to allocate 0x3000 bytes below 0xc0003000 the current code will allocate [0xc0001000-0xc0004000], not [0xc0000000-0xc0003000] like you would expect. - Matt ] Signed-off-by: Yinghai Lu <yinghai@kernel.org> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Mark Rutland <mark.rutland@arm.com> Cc: <stable@vger.kernel.org> Signed-off-by: Matt Fleming <matt.fleming@intel.com>
-rw-r--r--drivers/firmware/efi/libstub/efi-stub-helper.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 9bd9fbb5bea8..c927bccd92bd 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -170,12 +170,12 @@ again:
start = desc->phys_addr;
end = start + desc->num_pages * (1UL << EFI_PAGE_SHIFT);
- if ((start + size) > end || (start + size) > max)
- continue;
-
- if (end - size > max)
+ if (end > max)
end = max;
+ if ((start + size) > end)
+ continue;
+
if (round_down(end - size, align) < start)
continue;