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/uapi/video/uvesafb.h | 61 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) create mode 100644 include/uapi/video/uvesafb.h (limited to 'include/uapi/video/uvesafb.h') diff --git a/include/uapi/video/uvesafb.h b/include/uapi/video/uvesafb.h new file mode 100644 index 000000000..a0d5c9213 --- /dev/null +++ b/include/uapi/video/uvesafb.h @@ -0,0 +1,61 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_UVESAFB_H +#define _UAPI_UVESAFB_H + +#include + +struct v86_regs { + __u32 ebx; + __u32 ecx; + __u32 edx; + __u32 esi; + __u32 edi; + __u32 ebp; + __u32 eax; + __u32 eip; + __u32 eflags; + __u32 esp; + __u16 cs; + __u16 ss; + __u16 es; + __u16 ds; + __u16 fs; + __u16 gs; +}; + +/* Task flags */ +#define TF_VBEIB 0x01 +#define TF_BUF_ESDI 0x02 +#define TF_BUF_ESBX 0x04 +#define TF_BUF_RET 0x08 +#define TF_EXIT 0x10 + +struct uvesafb_task { + __u8 flags; + int buf_len; + struct v86_regs regs; +}; + +/* Constants for the capabilities field + * in vbe_ib */ +#define VBE_CAP_CAN_SWITCH_DAC 0x01 +#define VBE_CAP_VGACOMPAT 0x02 + +/* The VBE Info Block */ +struct vbe_ib { + char vbe_signature[4]; + __u16 vbe_version; + __u32 oem_string_ptr; + __u32 capabilities; + __u32 mode_list_ptr; + __u16 total_memory; + __u16 oem_software_rev; + __u32 oem_vendor_name_ptr; + __u32 oem_product_name_ptr; + __u32 oem_product_rev_ptr; + __u8 reserved[222]; + char oem_data[256]; + char misc_data[512]; +} __attribute__ ((packed)); + +#endif /* _UAPI_UVESAFB_H */ -- cgit v1.3.1