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 --- include/net/dsfield.h | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) create mode 100644 include/net/dsfield.h (limited to 'include/net/dsfield.h') diff --git a/include/net/dsfield.h b/include/net/dsfield.h new file mode 100644 index 000000000..a59a57ffc --- /dev/null +++ b/include/net/dsfield.h @@ -0,0 +1,53 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* include/net/dsfield.h - Manipulation of the Differentiated Services field */ + +/* Written 1998-2000 by Werner Almesberger, EPFL ICA */ + + +#ifndef __NET_DSFIELD_H +#define __NET_DSFIELD_H + +#include +#include +#include +#include + + +static inline __u8 ipv4_get_dsfield(const struct iphdr *iph) +{ + return iph->tos; +} + + +static inline __u8 ipv6_get_dsfield(const struct ipv6hdr *ipv6h) +{ + return ntohs(*(__force const __be16 *)ipv6h) >> 4; +} + + +static inline void ipv4_change_dsfield(struct iphdr *iph,__u8 mask, + __u8 value) +{ + __u32 check = ntohs((__force __be16)iph->check); + __u8 dsfield; + + dsfield = (iph->tos & mask) | value; + check += iph->tos; + if ((check+1) >> 16) check = (check+1) & 0xffff; + check -= dsfield; + check += check >> 16; /* adjust carry */ + iph->check = (__force __sum16)htons(check); + iph->tos = dsfield; +} + + +static inline void ipv6_change_dsfield(struct ipv6hdr *ipv6h,__u8 mask, + __u8 value) +{ + __be16 *p = (__force __be16 *)ipv6h; + + *p = (*p & htons((((u16)mask << 4) | 0xf00f))) | htons((u16)value << 4); +} + + +#endif -- cgit v1.3.1