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 --- samples/bpf/parse_ldabs.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 samples/bpf/parse_ldabs.c (limited to 'samples/bpf/parse_ldabs.c') diff --git a/samples/bpf/parse_ldabs.c b/samples/bpf/parse_ldabs.c new file mode 100644 index 000000000..c6f65f90a --- /dev/null +++ b/samples/bpf/parse_ldabs.c @@ -0,0 +1,43 @@ +/* Copyright (c) 2016 Facebook + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + */ +#define KBUILD_MODNAME "foo" +#include +#include +#include +#include +#include +#include +#include +#include "bpf_legacy.h" + +#define DEFAULT_PKTGEN_UDP_PORT 9 +#define IP_MF 0x2000 +#define IP_OFFSET 0x1FFF + +static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff) +{ + return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off)) + & (IP_MF | IP_OFFSET); +} + +SEC("ldabs") +int handle_ingress(struct __sk_buff *skb) +{ + __u64 troff = ETH_HLEN + sizeof(struct iphdr); + + if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP) + return 0; + if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP || + load_byte(skb, ETH_HLEN) != 0x45) + return 0; + if (ip_is_fragment(skb, ETH_HLEN)) + return 0; + if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT) + return TC_ACT_SHOT; + return 0; +} +char _license[] SEC("license") = "GPL"; -- cgit v1.3.1