From 09c79b60960bdd4b00916219402eabfa5e479c5a Mon Sep 17 00:00:00 2001 From: Jesper Juhl Date: Mon, 6 Feb 2012 20:07:04 +1100 Subject: [PATCH] mpi: Avoid using freed pointer in mpi_lshift_limbs() At the start of the function we assign 'a->d' to 'ap'. Then we use the RESIZE_IF_NEEDED macro on 'a' - this may free 'a->d' and replace it with newly allocaetd storage. In that case, we'll be operating on freed memory further down in the function when we index into 'ap[]'. Since we don't actually need 'ap' until after the use of the RESIZE_IF_NEEDED macro we can just delay the assignment to it until after we've potentially resized, thus avoiding the issue. While I was there anyway I also changed the integer variable 'n' to be const. It might as well be since we only assign to it once and use it as a constant, and then the compiler will tell us if we ever assign to it in the future. Signed-off-by: Jesper Juhl Acked-by: Dmitry Kasatkin Signed-off-by: James Morris --- lib/mpi/mpi-bit.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/lib/mpi/mpi-bit.c b/lib/mpi/mpi-bit.c index 2f526627e4f5..0c505361da19 100644 --- a/lib/mpi/mpi-bit.c +++ b/lib/mpi/mpi-bit.c @@ -177,8 +177,8 @@ int mpi_rshift(MPI x, MPI a, unsigned n) */ int mpi_lshift_limbs(MPI a, unsigned int count) { - mpi_ptr_t ap = a->d; - int n = a->nlimbs; + const int n = a->nlimbs; + mpi_ptr_t ap; int i; if (!count || !n) @@ -187,6 +187,7 @@ int mpi_lshift_limbs(MPI a, unsigned int count) if (RESIZE_IF_NEEDED(a, n + count) < 0) return -ENOMEM; + ap = a->d; for (i = n - 1; i >= 0; i--) ap[i + count] = ap[i]; for (i = 0; i < count; i++) -- 2.30.2