4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michal Marek <mmarek@xxxxxxxx>
commit 3ee0cb5fb5eea2110db1b5cb7f67029b7be8a376 upstream.
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: 0f74fbf77d45 ("MPI: Fix mpi_read_buffer")
Signed-off-by: Michal Marek <mmarek@xxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
lib/mpi/mpicoder.c | 39 +++++++++++++++++++++------------------
1 file changed, 21 insertions(+), 18 deletions(-)
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -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)
*
@@ -146,7 +163,7 @@ int mpi_read_buffer(MPI a, uint8_t *buf,
uint8_t *p;
mpi_limb_t alimb;
unsigned int n = mpi_get_size(a);
- int i, lzeros = 0;
+ int i, lzeros;
if (buf_len < n || !buf || !nbytes)
return -EINVAL;
@@ -154,14 +171,7 @@ int mpi_read_buffer(MPI a, uint8_t *buf,
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);
p = buf;
*nbytes = n - lzeros;
@@ -343,7 +353,7 @@ int mpi_write_to_sgl(MPI a, struct scatt
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 || *nbytes < n)
return -EINVAL;
@@ -351,14 +361,7 @@ int mpi_write_to_sgl(MPI a, struct scatt
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);
*nbytes = n - lzeros;
buf_len = sgl->length;
--
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