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Commit 3ee0cb5f authored by Michal Marek's avatar Michal Marek Committed by Herbert Xu
Browse files

lib/mpi: Endianness fix 



The limbs are integers in the host endianness, so we can't simply
iterate over the individual bytes. The current code happens to work on
little-endian, because the order of the limbs in the MPI array is the
same as the order of the bytes in each limb, but it breaks on
big-endian.

Fixes: 0f74fbf7 ("MPI: Fix mpi_read_buffer")
Signed-off-by: default avatarMichal Marek <mmarek@suse.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent bfd927ff

lib/mpi/mpicoder.c

+21 −18
Original line number Diff line number Diff line
@@ -128,6 +128,23 @@ MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread) 
}

EXPORT_SYMBOL_GPL(mpi_read_from_buffer);



static int count_lzeros(MPI a)

{

	mpi_limb_t alimb;

	int i, lzeros = 0;



	for (i = a->nlimbs - 1; i >= 0; i--) {

		alimb = a->d[i];

		if (alimb == 0) {

			lzeros += sizeof(mpi_limb_t);

		} else {

			lzeros += count_leading_zeros(alimb) / 8;

			break;

		}

	}

	return lzeros;

}



/**

 * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)

 *
@@ -148,7 +165,7 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, 
	uint8_t *p;

	mpi_limb_t alimb;

	unsigned int n = mpi_get_size(a);

	int i, lzeros = 0;

	int i, lzeros;



	if (!buf || !nbytes)

		return -EINVAL;
@@ -156,14 +173,7 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes, 
	if (sign)

		*sign = a->sign;



	p = (void *)&a->d[a->nlimbs] - 1;



	for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {

		if (!*p)

			lzeros++;

		else

			break;

	}

	lzeros = count_lzeros(a);



	if (buf_len < n - lzeros) {

		*nbytes = n - lzeros;
@@ -351,7 +361,7 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes, 
	u8 *p, *p2;

	mpi_limb_t alimb, alimb2;

	unsigned int n = mpi_get_size(a);

	int i, x, y = 0, lzeros = 0, buf_len;

	int i, x, y = 0, lzeros, buf_len;



	if (!nbytes)

		return -EINVAL;
@@ -359,14 +369,7 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes, 
	if (sign)

		*sign = a->sign;



	p = (void *)&a->d[a->nlimbs] - 1;



	for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {

		if (!*p)

			lzeros++;

		else

			break;

	}

	lzeros = count_lzeros(a);



	if (*nbytes < n - lzeros) {

		*nbytes = n - lzeros;