mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-25 13:14:07 +08:00
af0ead42f6
With CONFIG_CFI_CLANG, the compiler injects a type preamble immediately
before each function and a check to validate the target function type
before indirect calls:
; type preamble
.word <id>
function:
...
; indirect call check
lw t1, -4(a0)
lui t2, <hi20>
addiw t2, t2, <lo12>
beq t1, t2, .Ltmp0
ebreak
.Ltmp0:
jarl a0
Implement error handling code for the ebreak traps emitted for the
checks. This produces the following oops on a CFI failure (generated
using lkdtm):
[ 21.177245] CFI failure at lkdtm_indirect_call+0x22/0x32 [lkdtm]
(target: lkdtm_increment_int+0x0/0x18 [lkdtm]; expected type: 0x3ad55aca)
[ 21.178483] Kernel BUG [#1]
[ 21.178671] Modules linked in: lkdtm
[ 21.179037] CPU: 1 PID: 104 Comm: sh Not tainted
6.3.0-rc6-00037-g37d5ec6297ab #1
[ 21.179511] Hardware name: riscv-virtio,qemu (DT)
[ 21.179818] epc : lkdtm_indirect_call+0x22/0x32 [lkdtm]
[ 21.180106] ra : lkdtm_CFI_FORWARD_PROTO+0x48/0x7c [lkdtm]
[ 21.180426] epc : ffffffff01387092 ra : ffffffff01386f14 sp : ff20000000453cf0
[ 21.180792] gp : ffffffff81308c38 tp : ff6000000243f080 t0 : ff20000000453b78
[ 21.181157] t1 : 000000003ad55aca t2 : 000000007e0c52a5 s0 : ff20000000453d00
[ 21.181506] s1 : 0000000000000001 a0 : ffffffff0138d170 a1 : ffffffff013870bc
[ 21.181819] a2 : b5fea48dd89aa700 a3 : 0000000000000001 a4 : 0000000000000fff
[ 21.182169] a5 : 0000000000000004 a6 : 00000000000000b7 a7 : 0000000000000000
[ 21.182591] s2 : ff20000000453e78 s3 : ffffffffffffffea s4 : 0000000000000012
[ 21.183001] s5 : ff600000023c7000 s6 : 0000000000000006 s7 : ffffffff013882a0
[ 21.183653] s8 : 0000000000000008 s9 : 0000000000000002 s10: ffffffff0138d878
[ 21.184245] s11: ffffffff0138d878 t3 : 0000000000000003 t4 : 0000000000000000
[ 21.184591] t5 : ffffffff8133df08 t6 : ffffffff8133df07
[ 21.184858] status: 0000000000000120 badaddr: 0000000000000000
cause: 0000000000000003
[ 21.185415] [<ffffffff01387092>] lkdtm_indirect_call+0x22/0x32 [lkdtm]
[ 21.185772] [<ffffffff01386f14>] lkdtm_CFI_FORWARD_PROTO+0x48/0x7c [lkdtm]
[ 21.186093] [<ffffffff01383552>] lkdtm_do_action+0x22/0x34 [lkdtm]
[ 21.186445] [<ffffffff0138350c>] direct_entry+0x128/0x13a [lkdtm]
[ 21.186817] [<ffffffff8033ed8c>] full_proxy_write+0x58/0xb2
[ 21.187352] [<ffffffff801d4fe8>] vfs_write+0x14c/0x33a
[ 21.187644] [<ffffffff801d5328>] ksys_write+0x64/0xd4
[ 21.187832] [<ffffffff801d53a6>] sys_write+0xe/0x1a
[ 21.188171] [<ffffffff80003996>] ret_from_syscall+0x0/0x2
[ 21.188595] Code: 0513 0f65 a303 ffc5 53b7 7e0c 839b 2a53 0363 0073 (9002) 9582
[ 21.189178] ---[ end trace 0000000000000000 ]---
[ 21.189590] Kernel panic - not syncing: Fatal exception
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com> # ISA bits
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20230710183544.999540-12-samitolvanen@google.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
||
/*
|
||
* Clang Control Flow Integrity (CFI) support.
|
||
*
|
||
* Copyright (C) 2023 Google LLC
|
||
*/
|
||
#include <asm/cfi.h>
|
||
#include <asm/insn.h>
|
||
|
||
/*
|
||
* Returns the target address and the expected type when regs->epc points
|
||
* to a compiler-generated CFI trap.
|
||
*/
|
||
static bool decode_cfi_insn(struct pt_regs *regs, unsigned long *target,
|
||
u32 *type)
|
||
{
|
||
unsigned long *regs_ptr = (unsigned long *)regs;
|
||
int rs1_num;
|
||
u32 insn;
|
||
|
||
*target = *type = 0;
|
||
|
||
/*
|
||
* The compiler generates the following instruction sequence
|
||
* for indirect call checks:
|
||
*
|
||
* lw t1, -4(<reg>)
|
||
* lui t2, <hi20>
|
||
* addiw t2, t2, <lo12>
|
||
* beq t1, t2, .Ltmp1
|
||
* ebreak ; <- regs->epc
|
||
* .Ltmp1:
|
||
* jalr <reg>
|
||
*
|
||
* We can read the expected type and the target address from the
|
||
* registers passed to the beq/jalr instructions.
|
||
*/
|
||
if (get_kernel_nofault(insn, (void *)regs->epc - 4))
|
||
return false;
|
||
if (!riscv_insn_is_beq(insn))
|
||
return false;
|
||
|
||
*type = (u32)regs_ptr[RV_EXTRACT_RS1_REG(insn)];
|
||
|
||
if (get_kernel_nofault(insn, (void *)regs->epc) ||
|
||
get_kernel_nofault(insn, (void *)regs->epc + GET_INSN_LENGTH(insn)))
|
||
return false;
|
||
|
||
if (riscv_insn_is_jalr(insn))
|
||
rs1_num = RV_EXTRACT_RS1_REG(insn);
|
||
else if (riscv_insn_is_c_jalr(insn))
|
||
rs1_num = RVC_EXTRACT_C2_RS1_REG(insn);
|
||
else
|
||
return false;
|
||
|
||
*target = regs_ptr[rs1_num];
|
||
|
||
return true;
|
||
}
|
||
|
||
/*
|
||
* Checks if the ebreak trap is because of a CFI failure, and handles the trap
|
||
* if needed. Returns a bug_trap_type value similarly to report_bug.
|
||
*/
|
||
enum bug_trap_type handle_cfi_failure(struct pt_regs *regs)
|
||
{
|
||
unsigned long target;
|
||
u32 type;
|
||
|
||
if (!is_cfi_trap(regs->epc))
|
||
return BUG_TRAP_TYPE_NONE;
|
||
|
||
if (!decode_cfi_insn(regs, &target, &type))
|
||
return report_cfi_failure_noaddr(regs, regs->epc);
|
||
|
||
return report_cfi_failure(regs, regs->epc, &target, type);
|
||
}
|