From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nicolai Stange , Herbert Xu Subject: [PATCH 4.4 192/192] lib/mpi: mpi_write_sgl(): fix skipping of leading zero limbs Date: Mon, 12 Sep 2016 19:01:41 +0200 Message-Id: <20160912152207.694766774@linuxfoundation.org> In-Reply-To: <20160912152158.855601725@linuxfoundation.org> References: <20160912152158.855601725@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nicolai Stange 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 Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- lib/mpi/mpicoder.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) --- a/lib/mpi/mpicoder.c +++ b/lib/mpi/mpicoder.c @@ -367,7 +367,9 @@ int mpi_write_to_sgl(MPI a, struct scatt 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 scatt #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); }