On Tue, Dec 19, 2017 at 08:42:58PM -0800, Junaid Shahid wrote:
> The aesni_gcm_enc/dec functions can access memory before the start of
> the data buffer if the length of the data buffer is less than 16 bytes.
> This is because they perform the read via a single 16-byte load. This
> can potentially result in accessing a page that is not mapped and thus
> causing the machine to crash. This patch fixes that by reading the
> partial block byte-by-byte and optionally an via 8-byte load if the block
> was at least 8 bytes.
>
> Fixes: 0487ccac ("crypto: aesni - make non-AVX AES-GCM work with any aadlen")
> Signed-off-by: Junaid Shahid <junaids@xxxxxxxxxx>
Did you run the self-tests (boot with CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
unset)? The second patch causes them to start failing:
[ 1.169640] alg: aead: Test 7 failed on encryption for rfc4106-gcm-aesni
[ 1.178308] alg: aead: Test 4 failed on encryption for generic-gcm-aesni
Also, don't the AVX and AVX2 versions have the same bug? These patches only fix
the non-AVX version.
> +# read the last <16 byte block
> +# Clobbers %rax, DPTR, TMP1 and XMM1-2
> +.macro READ_PARTIAL_BLOCK DPTR DLEN TMP1 XMM1 XMM2 XMMDst
> + pxor \XMMDst, \XMMDst
> + mov \DLEN, \TMP1
> + cmp $8, \DLEN
> + jl _read_last_lt8_\@
> + mov (\DPTR), %rax
> + MOVQ_R64_XMM %rax, \XMMDst
> + add $8, \DPTR
> + sub $8, \TMP1
> + jz _done_read_last_partial_block_\@
> +_read_last_lt8_\@:
> + shl $8, %rax
> + mov -1(\DPTR, \TMP1, 1), %al
> + dec \TMP1
> + jnz _read_last_lt8_\@
> + MOVQ_R64_XMM %rax, \XMM1
Doesn't %rax needs to be zeroed at '_read_last_lt8' so that the padding is
zeroed?
> + # adjust the shuffle mask pointer to be able to shift either 0 or 8
> + # bytes depending on whether the last block is <8 bytes or not
> + mov \DLEN, \TMP1
> + and $8, \TMP1
> + lea SHIFT_MASK(%rip), %rax
> + sub \TMP1, %rax
> + movdqu (%rax), \XMM2 # get the appropriate shuffle mask
> + PSHUFB_XMM \XMM2, \XMM1 # shift left either 0 or 8 bytes
Is there any way this can be simplified to use pslldq? The shift is just 8
bytes or nothing, and we already had to branch earlier depending on whether we
needed to read the 8 bytes or not.
Eric
