From 78004e9a87f240df03e2f73120d291763c32e0a7 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Fri, 21 Aug 2026 01:45:27 +0000 Subject: openrisc: fix arbitrary kernel memory access via or1k_atomic syscall sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user pointers, v1 and v2, and swaps the words they point to in hand-written assembly. l.lwz r29,0(r4) l.lwz r27,0(r5) l.sw 0(r4),r27 l.sw 0(r5),r29 The pointers are not checked with access_ok(). The four memory accesses also have no exception table entries. A caller passes a kernel address as either pointer, and the syscall reads from and writes to it directly. This gives an unprivileged process a kernel read/write primitive. It overwrites kernel data such as the sys_call_table, gaining code execution in kernel context. Check both pointers before entering the critical section. Add fixups for the four memory accesses so faults on valid but unmapped user addresses return -EFAULT. [shorne@gmail.com: fix comment style] Fixes: 9d02a4283e9c ("OpenRISC: Boot code") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Stafford Horne --- lib/crypto/mpi/mpih-cmp.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 lib/crypto/mpi/mpih-cmp.c (limited to 'lib/crypto/mpi/mpih-cmp.c') diff --git a/lib/crypto/mpi/mpih-cmp.c b/lib/crypto/mpi/mpih-cmp.c new file mode 100644 index 000000000..f23709114 --- /dev/null +++ b/lib/crypto/mpi/mpih-cmp.c @@ -0,0 +1,43 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* mpihelp-sub.c - MPI helper functions + * Copyright (C) 1994, 1996 Free Software Foundation, Inc. + * Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc. + * + * This file is part of GnuPG. + * + * Note: This code is heavily based on the GNU MP Library. + * Actually it's the same code with only minor changes in the + * way the data is stored; this is to support the abstraction + * of an optional secure memory allocation which may be used + * to avoid revealing of sensitive data due to paging etc. + * The GNU MP Library itself is published under the LGPL; + * however I decided to publish this code under the plain GPL. + */ + +#include "mpi-internal.h" + +/**************** + * Compare OP1_PTR/OP1_SIZE with OP2_PTR/OP2_SIZE. + * There are no restrictions on the relative sizes of + * the two arguments. + * Return 1 if OP1 > OP2, 0 if they are equal, and -1 if OP1 < OP2. + */ +int mpihelp_cmp(mpi_ptr_t op1_ptr, mpi_ptr_t op2_ptr, mpi_size_t size) +{ + mpi_size_t i; + mpi_limb_t op1_word, op2_word; + + for (i = size - 1; i >= 0; i--) { + op1_word = op1_ptr[i]; + op2_word = op2_ptr[i]; + if (op1_word != op2_word) + goto diff; + } + return 0; + +diff: + /* This can *not* be simplified to + * op2_word - op2_word + * since that expression might give signed overflow. */ + return (op1_word > op2_word) ? 1 : -1; +} -- cgit v1.3.1