From: Herbert Xu herbert@gondor.apana.org.au
commit c8ea9fce2baf7b643384f36f29e4194fa40d33a6 upstream.
Sometimes mpi_powm will leak karactx because a memory allocation failure causes a bail-out that skips the freeing of karactx. This patch moves the freeing of karactx to the end of the function like everything else so that it can't be skipped.
Reported-by: syzbot+f7baccc38dcc1e094e77@syzkaller.appspotmail.com Fixes: cdec9cb5167a ("crypto: GnuPG based MPI lib - source files...") Cc: stable@vger.kernel.org Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Reviewed-by: Eric Biggers ebiggers@kernel.org Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- lib/mpi/mpi-pow.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
--- a/lib/mpi/mpi-pow.c +++ b/lib/mpi/mpi-pow.c @@ -37,6 +37,7 @@ int mpi_powm(MPI res, MPI base, MPI exp, MPI mod) { mpi_ptr_t mp_marker = NULL, bp_marker = NULL, ep_marker = NULL; + struct karatsuba_ctx karactx = {}; mpi_ptr_t xp_marker = NULL; mpi_ptr_t tspace = NULL; mpi_ptr_t rp, ep, mp, bp; @@ -164,13 +165,11 @@ int mpi_powm(MPI res, MPI base, MPI exp, int c; mpi_limb_t e; mpi_limb_t carry_limb; - struct karatsuba_ctx karactx;
xp = xp_marker = mpi_alloc_limb_space(2 * (msize + 1)); if (!xp) goto enomem;
- memset(&karactx, 0, sizeof karactx); negative_result = (ep[0] & 1) && base->sign;
i = esize - 1; @@ -295,8 +294,6 @@ int mpi_powm(MPI res, MPI base, MPI exp, if (mod_shift_cnt) mpihelp_rshift(rp, rp, rsize, mod_shift_cnt); MPN_NORMALIZE(rp, rsize); - - mpihelp_release_karatsuba_ctx(&karactx); }
if (negative_result && rsize) { @@ -313,6 +310,7 @@ int mpi_powm(MPI res, MPI base, MPI exp, leave: rc = 0; enomem: + mpihelp_release_karatsuba_ctx(&karactx); if (assign_rp) mpi_assign_limb_space(res, rp, size); if (mp_marker)