diff options
| author | Jesper Juhl <jj@chaosbits.net> | 2012-02-06 20:07:04 +1100 |
|---|---|---|
| committer | James Morris <james.l.morris@oracle.com> | 2012-04-18 12:14:28 +1000 |
| commit | 09c79b60960bdd4b00916219402eabfa5e479c5a (patch) | |
| tree | d8be1892ca81cbd194ac5e8c198f0f939d432257 /lib/mpi | |
| parent | 86812bb0de1a3758dc6c7aa01a763158a7c0638a (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')
| -rw-r--r-- | lib/mpi/mpi-bit.c | 5 |
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++) |