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[PATCH bpf v2] riscv, bpf: fix incorrect usage of BPF_TRAMP_F_ORIG_STACK

Menglong Dong posted 1 patch 1 month, 2 weeks ago 
arch/riscv/net/bpf_jit_comp64.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
[PATCH bpf v2] riscv, bpf: fix incorrect usage of BPF_TRAMP_F_ORIG_STACK
Posted by Menglong Dong 1 month, 2 weeks ago 
The usage of BPF_TRAMP_F_ORIG_STACK in __arch_prepare_bpf_trampoline() is
wrong, and it should be BPF_TRAMP_F_CALL_ORIG, which caused crash as
Andreas reported:

  Insufficient stack space to handle exception!
  Task stack:     [0xff20000000010000..0xff20000000014000]
  Overflow stack: [0xff600000ffdad070..0xff600000ffdae070]
  CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ #15 PREEMPT(voluntary)
  Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025
  epc : copy_from_kernel_nofault+0xa/0x198
   ra : bpf_probe_read_kernel+0x20/0x60
  epc : ffffffff802b732a ra : ffffffff801e6070 sp : ff2000000000ffe0
   gp : ffffffff82262ed0 tp : 0000000000000000 t0 : ffffffff80022320
   t1 : ffffffff801e6056 t2 : 0000000000000000 s0 : ff20000000010040
   s1 : 0000000000000008 a0 : ff20000000010050 a1 : ff60000083b3d320
   a2 : 0000000000000008 a3 : 0000000000000097 a4 : 0000000000000000
   a5 : 0000000000000000 a6 : 0000000000000021 a7 : 0000000000000003
   s2 : ff20000000010050 s3 : ff6000008459fc18 s4 : ff60000083b3d340
   s5 : ff20000000010060 s6 : 0000000000000000 s7 : ff20000000013aa8
   s8 : 0000000000000000 s9 : 0000000000008000 s10: 000000000058dcb0
   s11: 000000000058dca7 t3 : 000000006925116d t4 : ff6000008090f026
   t5 : 00007fff9b0cbaa8 t6 : 0000000000000016
  status: 0000000200000120 badaddr: 0000000000000000 cause: 8000000000000005
  Kernel panic - not syncing: Kernel stack overflow
  CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ #15 PREEMPT(voluntary)
  Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025
  Call Trace:
  [<ffffffff8001a1f8>] dump_backtrace+0x28/0x38
  [<ffffffff80002502>] show_stack+0x3a/0x50
  [<ffffffff800122be>] dump_stack_lvl+0x56/0x80
  [<ffffffff80012300>] dump_stack+0x18/0x22
  [<ffffffff80002abe>] vpanic+0xf6/0x328
  [<ffffffff80002d2e>] panic+0x3e/0x40
  [<ffffffff80019ef0>] handle_bad_stack+0x98/0xa0
  [<ffffffff801e6070>] bpf_probe_read_kernel+0x20/0x60

Just fix it.

Fixes: 47c9214dcbea ("bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME")
Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Closes: https://lore.kernel.org/bpf/874ipnkfvt.fsf@igel.home/
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
---
v2:
- merge the code
---
 arch/riscv/net/bpf_jit_comp64.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 5f9457e910e8..37888abee70c 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -1133,10 +1133,6 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 
 	store_args(nr_arg_slots, args_off, ctx);
 
-	/* skip to actual body of traced function */
-	if (flags & BPF_TRAMP_F_ORIG_STACK)
-		orig_call += RV_FENTRY_NINSNS * 4;
-
 	if (flags & BPF_TRAMP_F_CALL_ORIG) {
 		emit_imm(RV_REG_A0, ctx->insns ? (const s64)im : RV_MAX_COUNT_IMM, ctx);
 		ret = emit_call((const u64)__bpf_tramp_enter, true, ctx);
@@ -1171,6 +1167,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 	}
 
 	if (flags & BPF_TRAMP_F_CALL_ORIG) {
+		/* skip to actual body of traced function */
+		orig_call += RV_FENTRY_NINSNS * 4;
 		restore_args(min_t(int, nr_arg_slots, RV_MAX_REG_ARGS), args_off, ctx);
 		restore_stack_args(nr_arg_slots - RV_MAX_REG_ARGS, args_off, stk_arg_off, ctx);
 		ret = emit_call((const u64)orig_call, true, ctx);
-- 
2.52.0
Re: [PATCH bpf v2] riscv, bpf: fix incorrect usage of BPF_TRAMP_F_ORIG_STACK
Posted by Andreas Schwab 3 weeks, 5 days ago 
It's rc5 and this is still not merged.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."
Re: [PATCH bpf v2] riscv, bpf: fix incorrect usage of BPF_TRAMP_F_ORIG_STACK
Posted by Pu Lehui 1 month, 2 weeks ago 

On 2025/12/19 22:29, Menglong Dong wrote:
> The usage of BPF_TRAMP_F_ORIG_STACK in __arch_prepare_bpf_trampoline() is
> wrong, and it should be BPF_TRAMP_F_CALL_ORIG, which caused crash as
> Andreas reported:
> 
>    Insufficient stack space to handle exception!
>    Task stack:     [0xff20000000010000..0xff20000000014000]
>    Overflow stack: [0xff600000ffdad070..0xff600000ffdae070]
>    CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ #15 PREEMPT(voluntary)
>    Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025
>    epc : copy_from_kernel_nofault+0xa/0x198
>     ra : bpf_probe_read_kernel+0x20/0x60
>    epc : ffffffff802b732a ra : ffffffff801e6070 sp : ff2000000000ffe0
>     gp : ffffffff82262ed0 tp : 0000000000000000 t0 : ffffffff80022320
>     t1 : ffffffff801e6056 t2 : 0000000000000000 s0 : ff20000000010040
>     s1 : 0000000000000008 a0 : ff20000000010050 a1 : ff60000083b3d320
>     a2 : 0000000000000008 a3 : 0000000000000097 a4 : 0000000000000000
>     a5 : 0000000000000000 a6 : 0000000000000021 a7 : 0000000000000003
>     s2 : ff20000000010050 s3 : ff6000008459fc18 s4 : ff60000083b3d340
>     s5 : ff20000000010060 s6 : 0000000000000000 s7 : ff20000000013aa8
>     s8 : 0000000000000000 s9 : 0000000000008000 s10: 000000000058dcb0
>     s11: 000000000058dca7 t3 : 000000006925116d t4 : ff6000008090f026
>     t5 : 00007fff9b0cbaa8 t6 : 0000000000000016
>    status: 0000000200000120 badaddr: 0000000000000000 cause: 8000000000000005
>    Kernel panic - not syncing: Kernel stack overflow
>    CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ #15 PREEMPT(voluntary)
>    Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025
>    Call Trace:
>    [<ffffffff8001a1f8>] dump_backtrace+0x28/0x38
>    [<ffffffff80002502>] show_stack+0x3a/0x50
>    [<ffffffff800122be>] dump_stack_lvl+0x56/0x80
>    [<ffffffff80012300>] dump_stack+0x18/0x22
>    [<ffffffff80002abe>] vpanic+0xf6/0x328
>    [<ffffffff80002d2e>] panic+0x3e/0x40
>    [<ffffffff80019ef0>] handle_bad_stack+0x98/0xa0
>    [<ffffffff801e6070>] bpf_probe_read_kernel+0x20/0x60
> 
> Just fix it.
> 
> Fixes: 47c9214dcbea ("bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME")
> Reported-by: Andreas Schwab <schwab@linux-m68k.org>
> Closes: https://lore.kernel.org/bpf/874ipnkfvt.fsf@igel.home/
> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> ---
> v2:
> - merge the code
> ---
>   arch/riscv/net/bpf_jit_comp64.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> index 5f9457e910e8..37888abee70c 100644
> --- a/arch/riscv/net/bpf_jit_comp64.c
> +++ b/arch/riscv/net/bpf_jit_comp64.c
> @@ -1133,10 +1133,6 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
>   
>   	store_args(nr_arg_slots, args_off, ctx);
>   
> -	/* skip to actual body of traced function */
> -	if (flags & BPF_TRAMP_F_ORIG_STACK)

Oh, how did this weird flags get in here...

> -		orig_call += RV_FENTRY_NINSNS * 4;
> -
>   	if (flags & BPF_TRAMP_F_CALL_ORIG) {
>   		emit_imm(RV_REG_A0, ctx->insns ? (const s64)im : RV_MAX_COUNT_IMM, ctx);
>   		ret = emit_call((const u64)__bpf_tramp_enter, true, ctx);
> @@ -1171,6 +1167,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
>   	}
>   
>   	if (flags & BPF_TRAMP_F_CALL_ORIG) {
> +		/* skip to actual body of traced function */
> +		orig_call += RV_FENTRY_NINSNS * 4;


LGTM, let's revert it.

Reviewed-by: Pu Lehui <pulehui@huawei.com>

>   		restore_args(min_t(int, nr_arg_slots, RV_MAX_REG_ARGS), args_off, ctx);
>   		restore_stack_args(nr_arg_slots - RV_MAX_REG_ARGS, args_off, stk_arg_off, ctx);
>   		ret = emit_call((const u64)orig_call, true, ctx);
Re: [PATCH bpf v2] riscv, bpf: fix incorrect usage of BPF_TRAMP_F_ORIG_STACK
Posted by Menglong Dong 1 month, 2 weeks ago 
On 2025/12/20 10:59, Pu Lehui wrote:
> 
> On 2025/12/19 22:29, Menglong Dong wrote:
> > The usage of BPF_TRAMP_F_ORIG_STACK in __arch_prepare_bpf_trampoline() is
> > wrong, and it should be BPF_TRAMP_F_CALL_ORIG, which caused crash as
> > Andreas reported:
> > 
> >    Insufficient stack space to handle exception!
> >    Task stack:     [0xff20000000010000..0xff20000000014000]
> >    Overflow stack: [0xff600000ffdad070..0xff600000ffdae070]
> >    CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ #15 PREEMPT(voluntary)
> >    Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025
> >    epc : copy_from_kernel_nofault+0xa/0x198
> >     ra : bpf_probe_read_kernel+0x20/0x60
> >    epc : ffffffff802b732a ra : ffffffff801e6070 sp : ff2000000000ffe0
> >     gp : ffffffff82262ed0 tp : 0000000000000000 t0 : ffffffff80022320
> >     t1 : ffffffff801e6056 t2 : 0000000000000000 s0 : ff20000000010040
> >     s1 : 0000000000000008 a0 : ff20000000010050 a1 : ff60000083b3d320
> >     a2 : 0000000000000008 a3 : 0000000000000097 a4 : 0000000000000000
> >     a5 : 0000000000000000 a6 : 0000000000000021 a7 : 0000000000000003
> >     s2 : ff20000000010050 s3 : ff6000008459fc18 s4 : ff60000083b3d340
> >     s5 : ff20000000010060 s6 : 0000000000000000 s7 : ff20000000013aa8
> >     s8 : 0000000000000000 s9 : 0000000000008000 s10: 000000000058dcb0
> >     s11: 000000000058dca7 t3 : 000000006925116d t4 : ff6000008090f026
> >     t5 : 00007fff9b0cbaa8 t6 : 0000000000000016
> >    status: 0000000200000120 badaddr: 0000000000000000 cause: 8000000000000005
> >    Kernel panic - not syncing: Kernel stack overflow
> >    CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ #15 PREEMPT(voluntary)
> >    Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025
> >    Call Trace:
> >    [<ffffffff8001a1f8>] dump_backtrace+0x28/0x38
> >    [<ffffffff80002502>] show_stack+0x3a/0x50
> >    [<ffffffff800122be>] dump_stack_lvl+0x56/0x80
> >    [<ffffffff80012300>] dump_stack+0x18/0x22
> >    [<ffffffff80002abe>] vpanic+0xf6/0x328
> >    [<ffffffff80002d2e>] panic+0x3e/0x40
> >    [<ffffffff80019ef0>] handle_bad_stack+0x98/0xa0
> >    [<ffffffff801e6070>] bpf_probe_read_kernel+0x20/0x60
> > 
> > Just fix it.
> > 
> > Fixes: 47c9214dcbea ("bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME")
> > Reported-by: Andreas Schwab <schwab@linux-m68k.org>
> > Closes: https://lore.kernel.org/bpf/874ipnkfvt.fsf@igel.home/
> > Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> > ---
> > v2:
> > - merge the code
> > ---
> >   arch/riscv/net/bpf_jit_comp64.c | 6 ++----
> >   1 file changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> > index 5f9457e910e8..37888abee70c 100644
> > --- a/arch/riscv/net/bpf_jit_comp64.c
> > +++ b/arch/riscv/net/bpf_jit_comp64.c
> > @@ -1133,10 +1133,6 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
> >   
> >   	store_args(nr_arg_slots, args_off, ctx);
> >   
> > -	/* skip to actual body of traced function */
> > -	if (flags & BPF_TRAMP_F_ORIG_STACK)
> 
> Oh, how did this weird flags get in here...

It's my fault. I wanted to use BPF_TRAMP_F_CALL_ORIG here, and
a copy-paste mistake happen. They look a little similar :(

> 
> > -		orig_call += RV_FENTRY_NINSNS * 4;
> > -
> >   	if (flags & BPF_TRAMP_F_CALL_ORIG) {
> >   		emit_imm(RV_REG_A0, ctx->insns ? (const s64)im : RV_MAX_COUNT_IMM, ctx);
> >   		ret = emit_call((const u64)__bpf_tramp_enter, true, ctx);
> > @@ -1171,6 +1167,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
> >   	}
> >   
> >   	if (flags & BPF_TRAMP_F_CALL_ORIG) {
> > +		/* skip to actual body of traced function */
> > +		orig_call += RV_FENTRY_NINSNS * 4;
> 
> 
> LGTM, let's revert it.
> 
> Reviewed-by: Pu Lehui <pulehui@huawei.com>
> 
> >   		restore_args(min_t(int, nr_arg_slots, RV_MAX_REG_ARGS), args_off, ctx);
> >   		restore_stack_args(nr_arg_slots - RV_MAX_REG_ARGS, args_off, stk_arg_off, ctx);
> >   		ret = emit_call((const u64)orig_call, true, ctx);

Andreas suggested that we remove the variable "orig_call" and use
"func_addr + RV_FENTRY_NINSNS * 4" directly here. But I saw the V2
is already applied. Hmm...I think it doesn't matter.

Thanks!
Menglong Dong

> 
>
Re: [PATCH bpf v2] riscv, bpf: fix incorrect usage of BPF_TRAMP_F_ORIG_STACK
Posted by Pu Lehui 1 month, 2 weeks ago 

On 2025/12/20 15:33, Menglong Dong wrote:
> On 2025/12/20 10:59, Pu Lehui wrote:
>>
>> On 2025/12/19 22:29, Menglong Dong wrote:
>>> The usage of BPF_TRAMP_F_ORIG_STACK in __arch_prepare_bpf_trampoline() is
>>> wrong, and it should be BPF_TRAMP_F_CALL_ORIG, which caused crash as
>>> Andreas reported:
>>>
>>>     Insufficient stack space to handle exception!
>>>     Task stack:     [0xff20000000010000..0xff20000000014000]
>>>     Overflow stack: [0xff600000ffdad070..0xff600000ffdae070]
>>>     CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ #15 PREEMPT(voluntary)
>>>     Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025
>>>     epc : copy_from_kernel_nofault+0xa/0x198
>>>      ra : bpf_probe_read_kernel+0x20/0x60
>>>     epc : ffffffff802b732a ra : ffffffff801e6070 sp : ff2000000000ffe0
>>>      gp : ffffffff82262ed0 tp : 0000000000000000 t0 : ffffffff80022320
>>>      t1 : ffffffff801e6056 t2 : 0000000000000000 s0 : ff20000000010040
>>>      s1 : 0000000000000008 a0 : ff20000000010050 a1 : ff60000083b3d320
>>>      a2 : 0000000000000008 a3 : 0000000000000097 a4 : 0000000000000000
>>>      a5 : 0000000000000000 a6 : 0000000000000021 a7 : 0000000000000003
>>>      s2 : ff20000000010050 s3 : ff6000008459fc18 s4 : ff60000083b3d340
>>>      s5 : ff20000000010060 s6 : 0000000000000000 s7 : ff20000000013aa8
>>>      s8 : 0000000000000000 s9 : 0000000000008000 s10: 000000000058dcb0
>>>      s11: 000000000058dca7 t3 : 000000006925116d t4 : ff6000008090f026
>>>      t5 : 00007fff9b0cbaa8 t6 : 0000000000000016
>>>     status: 0000000200000120 badaddr: 0000000000000000 cause: 8000000000000005
>>>     Kernel panic - not syncing: Kernel stack overflow
>>>     CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ #15 PREEMPT(voluntary)
>>>     Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025
>>>     Call Trace:
>>>     [<ffffffff8001a1f8>] dump_backtrace+0x28/0x38
>>>     [<ffffffff80002502>] show_stack+0x3a/0x50
>>>     [<ffffffff800122be>] dump_stack_lvl+0x56/0x80
>>>     [<ffffffff80012300>] dump_stack+0x18/0x22
>>>     [<ffffffff80002abe>] vpanic+0xf6/0x328
>>>     [<ffffffff80002d2e>] panic+0x3e/0x40
>>>     [<ffffffff80019ef0>] handle_bad_stack+0x98/0xa0
>>>     [<ffffffff801e6070>] bpf_probe_read_kernel+0x20/0x60
>>>
>>> Just fix it.
>>>
>>> Fixes: 47c9214dcbea ("bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME")
>>> Reported-by: Andreas Schwab <schwab@linux-m68k.org>
>>> Closes: https://lore.kernel.org/bpf/874ipnkfvt.fsf@igel.home/
>>> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
>>> ---
>>> v2:
>>> - merge the code
>>> ---
>>>    arch/riscv/net/bpf_jit_comp64.c | 6 ++----
>>>    1 file changed, 2 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
>>> index 5f9457e910e8..37888abee70c 100644
>>> --- a/arch/riscv/net/bpf_jit_comp64.c
>>> +++ b/arch/riscv/net/bpf_jit_comp64.c
>>> @@ -1133,10 +1133,6 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
>>>    
>>>    	store_args(nr_arg_slots, args_off, ctx);
>>>    
>>> -	/* skip to actual body of traced function */
>>> -	if (flags & BPF_TRAMP_F_ORIG_STACK)
>>
>> Oh, how did this weird flags get in here...
> 
> It's my fault. I wanted to use BPF_TRAMP_F_CALL_ORIG here, and
> a copy-paste mistake happen. They look a little similar :(
> 
>>
>>> -		orig_call += RV_FENTRY_NINSNS * 4;
>>> -
>>>    	if (flags & BPF_TRAMP_F_CALL_ORIG) {
>>>    		emit_imm(RV_REG_A0, ctx->insns ? (const s64)im : RV_MAX_COUNT_IMM, ctx);
>>>    		ret = emit_call((const u64)__bpf_tramp_enter, true, ctx);
>>> @@ -1171,6 +1167,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
>>>    	}
>>>    
>>>    	if (flags & BPF_TRAMP_F_CALL_ORIG) {
>>> +		/* skip to actual body of traced function */
>>> +		orig_call += RV_FENTRY_NINSNS * 4;
>>
>>
>> LGTM, let's revert it.
>>
>> Reviewed-by: Pu Lehui <pulehui@huawei.com>
>>
>>>    		restore_args(min_t(int, nr_arg_slots, RV_MAX_REG_ARGS), args_off, ctx);
>>>    		restore_stack_args(nr_arg_slots - RV_MAX_REG_ARGS, args_off, stk_arg_off, ctx);
>>>    		ret = emit_call((const u64)orig_call, true, ctx);
> 
> Andreas suggested that we remove the variable "orig_call" and use
> "func_addr + RV_FENTRY_NINSNS * 4" directly here. But I saw the V2
> is already applied. Hmm...I think it doesn't matter.

no warries. looks nice.

> 
> Thanks!
> Menglong Dong
> 
>>
>>
> 
> 
> 
> 
> 
>

Patchew 2.1-devel-b67e4c2

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