Commit c8ea9fce authored by Herbert Xu's avatar Herbert Xu

lib/mpi: Fix karactx leak in mpi_powm

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: cdec9cb5 ("crypto: GnuPG based MPI lib - source files...")
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: default avatarEric Biggers <ebiggers@kernel.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 7829a0c1
......@@ -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;
......@@ -163,13 +164,11 @@ int mpi_powm(MPI res, MPI base, MPI exp, MPI mod)
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;
......@@ -294,8 +293,6 @@ int mpi_powm(MPI res, MPI base, MPI exp, MPI mod)
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) {
......@@ -312,6 +309,7 @@ int mpi_powm(MPI res, MPI base, MPI exp, MPI mod)
leave:
rc = 0;
enomem:
mpihelp_release_karatsuba_ctx(&karactx);
if (assign_rp)
mpi_assign_limb_space(res, rp, size);
if (mp_marker)
......
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