From: Guo Ren guoren@linux.alibaba.com
[ Upstream commit 87f48c7ccc73afc78630530d9af51f458f58cab8 ]
The kernel would panic when probed for an illegal position. eg:
(CONFIG_RISCV_ISA_C=n)
echo 'p:hello kernel_clone+0x16 a0=%a0' >> kprobe_events echo 1 > events/kprobes/hello/enable cat trace
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: __do_sys_newfstatat+0xb8/0xb8 CPU: 0 PID: 111 Comm: sh Not tainted 6.2.0-rc1-00027-g2d398fe49a4d #490 Hardware name: riscv-virtio,qemu (DT) Call Trace: [<ffffffff80007268>] dump_backtrace+0x38/0x48 [<ffffffff80c5e83c>] show_stack+0x50/0x68 [<ffffffff80c6da28>] dump_stack_lvl+0x60/0x84 [<ffffffff80c6da6c>] dump_stack+0x20/0x30 [<ffffffff80c5ecf4>] panic+0x160/0x374 [<ffffffff80c6db94>] generic_handle_arch_irq+0x0/0xa8 [<ffffffff802deeb0>] sys_newstat+0x0/0x30 [<ffffffff800158c0>] sys_clone+0x20/0x30 [<ffffffff800039e8>] ret_from_syscall+0x0/0x4 ---[ end Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: __do_sys_newfstatat+0xb8/0xb8 ]---
That is because the kprobe's ebreak instruction broke the kernel's original code. The user should guarantee the correction of the probe position, but it couldn't make the kernel panic.
This patch adds arch_check_kprobe in arch_prepare_kprobe to prevent an illegal position (Such as the middle of an instruction).
Fixes: c22b0bcb1dd0 ("riscv: Add kprobes supported") Signed-off-by: Guo Ren guoren@linux.alibaba.com Signed-off-by: Guo Ren guoren@kernel.org Reviewed-by: Björn Töpel bjorn@kernel.org Link: https://lore.kernel.org/r/20230201040604.3390509-1-guoren@kernel.org Signed-off-by: Palmer Dabbelt palmer@rivosinc.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/kernel/probes/kprobes.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c index e6e950b7cf32..388ecada500c 100644 --- a/arch/riscv/kernel/probes/kprobes.c +++ b/arch/riscv/kernel/probes/kprobes.c @@ -48,6 +48,21 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) post_kprobe_handler(p, kcb, regs); }
+static bool __kprobes arch_check_kprobe(struct kprobe *p) +{ + unsigned long tmp = (unsigned long)p->addr - p->offset; + unsigned long addr = (unsigned long)p->addr; + + while (tmp <= addr) { + if (tmp == addr) + return true; + + tmp += GET_INSN_LENGTH(*(u16 *)tmp); + } + + return false; +} + int __kprobes arch_prepare_kprobe(struct kprobe *p) { unsigned long probe_addr = (unsigned long)p->addr; @@ -55,6 +70,9 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) if (probe_addr & 0x1) return -EILSEQ;
+ if (!arch_check_kprobe(p)) + return -EILSEQ; + /* copy instruction */ p->opcode = *p->addr;