Messages in this thread | | | From | Guo Ren <> | Date | Sat, 28 Jan 2023 11:46:09 +0800 | Subject | Re: [PATCH] riscv: kprobe: Fixup kernel panic when probing an illegal position |
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On Sat, Jan 28, 2023 at 10:55 AM liaochang (A) <liaochang1@huawei.com> wrote: > > > > 在 2023/1/26 21:05, guoren@kernel.org 写道: > > From: Guo Ren <guoren@linux.alibaba.com> > > > > 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> > > --- > > 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 f21592d20306..475989f06d6d 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(*(kprobe_opcode_t *)tmp); > > + } > > + > > + return false; > > +} > > LGTM. > > I have submit a patch to fix the same problem, found at: Oh, I missed that patch. Our goal is the same.
But it would be best if you reused p->offset, not kallsyms_lookup_size_offset, the p->addr added by _kprobe_addr (kernel/kprobes.c), not just kallsyms_lookup_size_offset. Sure, it works around for the current riscv, but that's not correct.
> > https://lore.kernel.org/lkml/20230127130541.1250865-11-chenguokai17@mails.ucas.ac.cn/ > > So this boundary check is necessary no matter CONFIG_RISCV_ISA_C is enable or not, right? Yes, my panic example in the commit log is based on the !CONFIG_RISCV_ISA_C, you couldn't miss that.
> > > > + > > 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; > > > > -- > BR, > Liao, Chang
-- Best Regards Guo Ren
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