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 --- arch/mips/lib/uncached.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 arch/mips/lib/uncached.c (limited to 'arch/mips/lib/uncached.c') diff --git a/arch/mips/lib/uncached.c b/arch/mips/lib/uncached.c new file mode 100644 index 000000000..f80a67c09 --- /dev/null +++ b/arch/mips/lib/uncached.c @@ -0,0 +1,82 @@ +/* + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Copyright (C) 2005 Thiemo Seufer + * Copyright (C) 2005 MIPS Technologies, Inc. All rights reserved. + * Author: Maciej W. Rozycki + */ + + +#include +#include +#include + +#ifndef CKSEG2 +#define CKSEG2 CKSSEG +#endif +#ifndef TO_PHYS_MASK +#define TO_PHYS_MASK -1 +#endif + +/* + * FUNC is executed in one of the uncached segments, depending on its + * original address as follows: + * + * 1. If the original address is in CKSEG0 or CKSEG1, then the uncached + * segment used is CKSEG1. + * 2. If the original address is in XKPHYS, then the uncached segment + * used is XKPHYS(2). + * 3. Otherwise it's a bug. + * + * The same remapping is done with the stack pointer. Stack handling + * works because we don't handle stack arguments or more complex return + * values, so we can avoid sharing the same stack area between a cached + * and the uncached mode. + */ +unsigned long run_uncached(void *func) +{ + register long ret __asm__("$2"); + long lfunc = (long)func, ufunc; + long usp; + long sp; + + __asm__("move %0, $sp" : "=r" (sp)); + + if (sp >= (long)CKSEG0 && sp < (long)CKSEG2) + usp = CKSEG1ADDR(sp); +#ifdef CONFIG_64BIT + else if ((long long)sp >= (long long)PHYS_TO_XKPHYS(0, 0) && + (long long)sp < (long long)PHYS_TO_XKPHYS(8, 0)) + usp = PHYS_TO_XKPHYS(K_CALG_UNCACHED, + XKPHYS_TO_PHYS((long long)sp)); +#endif + else { + BUG(); + usp = sp; + } + if (lfunc >= (long)CKSEG0 && lfunc < (long)CKSEG2) + ufunc = CKSEG1ADDR(lfunc); +#ifdef CONFIG_64BIT + else if ((long long)lfunc >= (long long)PHYS_TO_XKPHYS(0, 0) && + (long long)lfunc < (long long)PHYS_TO_XKPHYS(8, 0)) + ufunc = PHYS_TO_XKPHYS(K_CALG_UNCACHED, + XKPHYS_TO_PHYS((long long)lfunc)); +#endif + else { + BUG(); + ufunc = lfunc; + } + + __asm__ __volatile__ ( + " move $16, $sp\n" + " move $sp, %1\n" + " jalr %2\n" + " move $sp, $16" + : "=r" (ret) + : "r" (usp), "r" (ufunc) + : "$16", "$31"); + + return ret; +} -- cgit v1.3.1