openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

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 <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/net/ipv6/exthdrs_offload.c b/net/ipv6/exthdrs_offload.c
new file mode 100644
index 000000000..4c00398f4
--- /dev/null
+++ b/net/ipv6/exthdrs_offload.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	IPV6 GSO/GRO offload support
+ *	Linux INET6 implementation
+ *
+ *      IPV6 Extension Header GSO/GRO support
+ */
+#include <net/protocol.h>
+#include "ip6_offload.h"
+
+static const struct net_offload rthdr_offload = {
+	.flags		=	INET6_PROTO_GSO_EXTHDR,
+};
+
+static const struct net_offload dstopt_offload = {
+	.flags		=	INET6_PROTO_GSO_EXTHDR,
+};
+
+static const struct net_offload hbh_offload = {
+	.flags		=	INET6_PROTO_GSO_EXTHDR,
+};
+
+int __init ipv6_exthdrs_offload_init(void)
+{
+	int ret;
+
+	ret = inet6_add_offload(&rthdr_offload, IPPROTO_ROUTING);
+	if (ret)
+		goto out;
+
+	ret = inet6_add_offload(&dstopt_offload, IPPROTO_DSTOPTS);
+	if (ret)
+		goto out_rt;
+
+	ret = inet6_add_offload(&hbh_offload, IPPROTO_HOPOPTS);
+	if (ret)
+		goto out_dstopts;
+
+out:
+	return ret;
+
+out_dstopts:
+	inet6_del_offload(&dstopt_offload, IPPROTO_DSTOPTS);
+
+out_rt:
+	inet6_del_offload(&rthdr_offload, IPPROTO_ROUTING);
+	goto out;
+}