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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: 0f74fbf77d ("MPI: Fix mpi_read_buffer")
Signed-off-by: Michal Marek <mmarek@suse.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Michal Marek 2016-02-17 14:46:59 +01:00 committed by Herbert Xu
parent bfd927ffa2
commit 3ee0cb5fb5
1 changed files with 21 additions and 18 deletions
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39
lib/mpi/mpicoder.c
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@ -128,6 +128,23 @@ leave:
}
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;