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authorNicolai Stange <nicstange@gmail.com>2016-03-22 13:12:35 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-09-15 08:27:54 +0200
commit11c27e850d90372d79c1337be299923b5fb353e8 (patch)
tree068c6da3a091106169bf63ed1e472a165adf7c21 /lib/mpi
parent3838b04f6d5868f5ec5ee52ce1391b6253c6ce16 (diff)
downloadlinux-linaro-stable-11c27e850d90372d79c1337be299923b5fb353e8.tar.gz
lib/mpi: mpi_write_sgl(): fix skipping of leading zero limbs
commit f2d1362ff7d266b3d2b1c764d6c2ef4a3b457f23 upstream. Currently, if the number of leading zeros is greater than fits into a complete limb, mpi_write_sgl() skips them by iterating over them limb-wise. However, it fails to adjust its internal leading zeros tracking variable, lzeros, accordingly: it does a p -= sizeof(alimb); continue; which should really have been a lzeros -= sizeof(alimb); continue; Since lzeros never decreases if its initial value >= sizeof(alimb), nothing gets copied by mpi_write_sgl() in that case. Instead of skipping the high order zero limbs within the loop as shown above, fix the issue by adjusting the copying loop's bounds. Fixes: 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib/mpi')
-rw-r--r--lib/mpi/mpicoder.c21
1 files changed, 9 insertions, 12 deletions
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index e00ff00e861c..e37dbf53e226 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -367,7 +367,9 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
buf_len = sgl->length;
p2 = sg_virt(sgl);
- for (i = a->nlimbs - 1; i >= 0; i--) {
+ for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
+ lzeros %= BYTES_PER_MPI_LIMB;
+ i >= 0; i--) {
alimb = a->d[i];
p = (u8 *)&alimb2;
#if BYTES_PER_MPI_LIMB == 4
@@ -388,17 +390,12 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
#error please implement for this limb size.
#endif
if (lzeros > 0) {
- if (lzeros >= sizeof(alimb)) {
- p -= sizeof(alimb);
- continue;
- } else {
- mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
- mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
- + lzeros;
- *limb1 = *limb2;
- p -= lzeros;
- y = lzeros;
- }
+ mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
+ mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
+ + lzeros;
+ *limb1 = *limb2;
+ p -= lzeros;
+ y = lzeros;
lzeros -= sizeof(alimb);
}