From 12316538b1d193064109ce1a28fc9bacd43950de Mon Sep 17 00:00:00 2001 From: Guo Ren Date: Tue, 31 Jan 2023 23:06:04 -0500 Subject: riscv: kprobe: Fixup kernel panic when probing an illegal position [ 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: [] dump_backtrace+0x38/0x48 [] show_stack+0x50/0x68 [] dump_stack_lvl+0x60/0x84 [] dump_stack+0x20/0x30 [] panic+0x160/0x374 [] generic_handle_arch_irq+0x0/0xa8 [] sys_newstat+0x0/0x30 [] sys_clone+0x20/0x30 [] 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 Signed-off-by: Guo Ren Reviewed-by: Björn Töpel Link: https://lore.kernel.org/r/20230201040604.3390509-1-guoren@kernel.org Signed-off-by: Palmer Dabbelt Signed-off-by: Sasha Levin --- arch/riscv/kernel/probes/kprobes.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'arch/riscv/kernel') 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; -- cgit v1.2.3