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/powerpc/boot/of.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 arch/powerpc/boot/of.c (limited to 'arch/powerpc/boot/of.c') diff --git a/arch/powerpc/boot/of.c b/arch/powerpc/boot/of.c new file mode 100644 index 000000000..2fbd4ae60 --- /dev/null +++ b/arch/powerpc/boot/of.c @@ -0,0 +1,93 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) Paul Mackerras 1997. + */ +#include +#include +#include "types.h" +#include "elf.h" +#include "string.h" +#include "stdio.h" +#include "page.h" +#include "ops.h" + +#include "of.h" + +/* Value picked to match that used by yaboot */ +#define PROG_START 0x01400000 /* only used on 64-bit systems */ +#define RAM_END (512<<20) /* Fixme: use OF */ +#define ONE_MB 0x100000 + + + +static unsigned long claim_base; + +void epapr_platform_init(unsigned long r3, unsigned long r4, unsigned long r5, + unsigned long r6, unsigned long r7); + +static void *of_try_claim(unsigned long size) +{ + unsigned long addr = 0; + + if (claim_base == 0) + claim_base = _ALIGN_UP((unsigned long)_end, ONE_MB); + + for(; claim_base < RAM_END; claim_base += ONE_MB) { +#ifdef DEBUG + printf(" trying: 0x%08lx\n\r", claim_base); +#endif + addr = (unsigned long) of_claim(claim_base, size, 0); + if (addr != PROM_ERROR) + break; + } + if (addr == 0) + return NULL; + claim_base = PAGE_ALIGN(claim_base + size); + return (void *)addr; +} + +static void of_image_hdr(const void *hdr) +{ + const Elf64_Ehdr *elf64 = hdr; + + if (elf64->e_ident[EI_CLASS] == ELFCLASS64) { + /* + * Maintain a "magic" minimum address. This keeps some older + * firmware platforms running. + */ + if (claim_base < PROG_START) + claim_base = PROG_START; + } +} + +static void of_platform_init(unsigned long a1, unsigned long a2, void *promptr) +{ + platform_ops.image_hdr = of_image_hdr; + platform_ops.malloc = of_try_claim; + platform_ops.exit = of_exit; + platform_ops.vmlinux_alloc = of_vmlinux_alloc; + + dt_ops.finddevice = of_finddevice; + dt_ops.getprop = of_getprop; + dt_ops.setprop = of_setprop; + + of_console_init(); + + of_init(promptr); + loader_info.promptr = promptr; + if (a1 && a2 && a2 != 0xdeadbeef) { + loader_info.initrd_addr = a1; + loader_info.initrd_size = a2; + } +} + +void platform_init(unsigned long r3, unsigned long r4, unsigned long r5, + unsigned long r6, unsigned long r7) +{ + /* Detect OF vs. ePAPR boot */ + if (r5) + of_platform_init(r3, r4, (void *)r5); + else + epapr_platform_init(r3, r4, r5, r6, r7); +} + -- cgit v1.3.1