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Commit c8ea9fce authored by Herbert Xu's avatar Herbert Xu
Browse files

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: default avatar <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

lib/mpi/mpi-pow.c

+2 −4
Original line number Diff line number Diff line
@@ -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)