path: root/lib/mpi
diff options
authorJesper Juhl <jj@chaosbits.net>2012-02-06 20:07:04 +1100
committerJames Morris <james.l.morris@oracle.com>2012-04-18 12:14:28 +1000
commit09c79b60960bdd4b00916219402eabfa5e479c5a (patch)
treed8be1892ca81cbd194ac5e8c198f0f939d432257 /lib/mpi
parent86812bb0de1a3758dc6c7aa01a763158a7c0638a (diff)
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 <jj@chaosbits.net> Acked-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'lib/mpi')
1 files 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++)