From: Guo Ren <[email protected]>
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 <[email protected]>
Signed-off-by: Guo Ren <[email protected]>
---
Changelog
V2:
- Fixup misaligned load (Thx Bjorn)
---
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..41c7481afde3 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;
--
2.36.1
[email protected] writes:
> From: Guo Ren <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Guo Ren <[email protected]>
> ---
> Changelog
> V2:
> - Fixup misaligned load (Thx Bjorn)
Reviewed-by: Björn Töpel <[email protected]>
Hello:
This patch was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <[email protected]>:
On Tue, 31 Jan 2023 23:06:04 -0500 you wrote:
> From: Guo Ren <[email protected]>
>
> 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
>
> [...]
Here is the summary with links:
- [V2] riscv: kprobe: Fixup kernel panic when probing an illegal position
https://git.kernel.org/riscv/c/87f48c7ccc73
You are awesome, thank you!
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