bpf: test_bpf: turn of preemption in function __run_once

Message ID 20190221084425.9574-1-anders.roxell@linaro.org
State Superseded
Headers show
Series
  • bpf: test_bpf: turn of preemption in function __run_once
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Commit Message

Anders Roxell Feb. 21, 2019, 8:44 a.m.
When running test seccomp_bpf the following splat occurs:

[ RUN      ] global.secseccomp_bpf.c:2136:global.detect_seccomp_filter_flags:Expected 22 (22) == (*__errno_location ()) (14)
seccomp_bpf.c:2138:global.detect_seccomp_filter_flags:Failed to detect that an unknown
  filter flag (0x8) is unsupported! Does a new flag need to be added to this test?
[ 2155.677841] BUG: assuming atomic context at kernel/seccomp.c:271
[ 2155.689351] in_atomic(): 0, irqs_disabled(): 0, pid: 28540, name: seccomp_bpf
[ 2155.696597] INFO: lockdep is turned off.
[ 2155.700605] CPU: 5 PID: 28540 Comm: seccomp_bpf Tainted: G        W         5.0.0-rc7-next-20190220 #1
[ 2155.709972] Hardware name: HiKey Development Board (DT)
[ 2155.715232] Call trace:
[ 2155.717710]  dump_backtrace+0x0/0x160
[ 2155.721399]  show_stack+0x24/0x30
[ 2155.724742]  dump_stack+0xc8/0x114
[ 2155.728172]  __cant_sleep+0xf0/0x108
[ 2155.731777]  __seccomp_filter+0x8c/0x5c8
[ 2155.735727]  __secure_computing+0x4c/0xe8
[ 2155.739767]  syscall_trace_enter+0xf8/0x2b8
[ 2155.743982]  el0_svc_common+0xf0/0x130
[ 2155.747758]  el0_svc_handler+0x38/0x78
[ 2155.751534]  el0_svc+0x8/0xc

Rework so that preemption is disabled when we loop over function
'BPF_PROG_RUN(...)'.
Commit 568f196756ad ("bpf: check that BPF programs run with preemption disabled")
highlighted the issue.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

---
 lib/test_bpf.c | 2 ++
 1 file changed, 2 insertions(+)

-- 
2.11.0

Comments

Daniel Borkmann Feb. 21, 2019, 3:37 p.m. | #1
On 02/21/2019 09:44 AM, Anders Roxell wrote:
> When running test seccomp_bpf the following splat occurs:

> 

> [ RUN      ] global.secseccomp_bpf.c:2136:global.detect_seccomp_filter_flags:Expected 22 (22) == (*__errno_location ()) (14)

> seccomp_bpf.c:2138:global.detect_seccomp_filter_flags:Failed to detect that an unknown

>   filter flag (0x8) is unsupported! Does a new flag need to be added to this test?

> [ 2155.677841] BUG: assuming atomic context at kernel/seccomp.c:271

> [ 2155.689351] in_atomic(): 0, irqs_disabled(): 0, pid: 28540, name: seccomp_bpf

> [ 2155.696597] INFO: lockdep is turned off.

> [ 2155.700605] CPU: 5 PID: 28540 Comm: seccomp_bpf Tainted: G        W         5.0.0-rc7-next-20190220 #1

> [ 2155.709972] Hardware name: HiKey Development Board (DT)

> [ 2155.715232] Call trace:

> [ 2155.717710]  dump_backtrace+0x0/0x160

> [ 2155.721399]  show_stack+0x24/0x30

> [ 2155.724742]  dump_stack+0xc8/0x114

> [ 2155.728172]  __cant_sleep+0xf0/0x108

> [ 2155.731777]  __seccomp_filter+0x8c/0x5c8

> [ 2155.735727]  __secure_computing+0x4c/0xe8

> [ 2155.739767]  syscall_trace_enter+0xf8/0x2b8

> [ 2155.743982]  el0_svc_common+0xf0/0x130

> [ 2155.747758]  el0_svc_handler+0x38/0x78

> [ 2155.751534]  el0_svc+0x8/0xc

> 

> Rework so that preemption is disabled when we loop over function

> 'BPF_PROG_RUN(...)'.

> Commit 568f196756ad ("bpf: check that BPF programs run with preemption disabled")

> highlighted the issue.

> 

> Suggested-by: Arnd Bergmann <arnd@arndb.de>

> Signed-off-by: Anders Roxell <anders.roxell@linaro.org>


Hmm, wrong commit description? Below code is not related to seccomp
but rather BPF test suite. Could you fix it up and resubmit? Rest
looks okay to me.

> ---

>  lib/test_bpf.c | 2 ++

>  1 file changed, 2 insertions(+)

> 

> diff --git a/lib/test_bpf.c b/lib/test_bpf.c

> index f3e570722a7e..0845f635f404 100644

> --- a/lib/test_bpf.c

> +++ b/lib/test_bpf.c

> @@ -6668,12 +6668,14 @@ static int __run_one(const struct bpf_prog *fp, const void *data,

>  	u64 start, finish;

>  	int ret = 0, i;

>  

> +	preempt_disable();

>  	start = ktime_get_ns();

>  

>  	for (i = 0; i < runs; i++)

>  		ret = BPF_PROG_RUN(fp, data);

>  

>  	finish = ktime_get_ns();

> +	preempt_enable();

>  

>  	*duration = finish - start;

>  	do_div(*duration, runs);

>
Anders Roxell Feb. 22, 2019, 8:25 a.m. | #2
On Thu, 21 Feb 2019 at 16:38, Daniel Borkmann <daniel@iogearbox.net> wrote:
>

> On 02/21/2019 09:44 AM, Anders Roxell wrote:

> > When running test seccomp_bpf the following splat occurs:

> >

> > [ RUN      ] global.secseccomp_bpf.c:2136:global.detect_seccomp_filter_flags:Expected 22 (22) == (*__errno_location ()) (14)

> > seccomp_bpf.c:2138:global.detect_seccomp_filter_flags:Failed to detect that an unknown

> >   filter flag (0x8) is unsupported! Does a new flag need to be added to this test?

> > [ 2155.677841] BUG: assuming atomic context at kernel/seccomp.c:271

> > [ 2155.689351] in_atomic(): 0, irqs_disabled(): 0, pid: 28540, name: seccomp_bpf

> > [ 2155.696597] INFO: lockdep is turned off.

> > [ 2155.700605] CPU: 5 PID: 28540 Comm: seccomp_bpf Tainted: G        W         5.0.0-rc7-next-20190220 #1

> > [ 2155.709972] Hardware name: HiKey Development Board (DT)

> > [ 2155.715232] Call trace:

> > [ 2155.717710]  dump_backtrace+0x0/0x160

> > [ 2155.721399]  show_stack+0x24/0x30

> > [ 2155.724742]  dump_stack+0xc8/0x114

> > [ 2155.728172]  __cant_sleep+0xf0/0x108

> > [ 2155.731777]  __seccomp_filter+0x8c/0x5c8

> > [ 2155.735727]  __secure_computing+0x4c/0xe8

> > [ 2155.739767]  syscall_trace_enter+0xf8/0x2b8

> > [ 2155.743982]  el0_svc_common+0xf0/0x130

> > [ 2155.747758]  el0_svc_handler+0x38/0x78

> > [ 2155.751534]  el0_svc+0x8/0xc

> >

> > Rework so that preemption is disabled when we loop over function

> > 'BPF_PROG_RUN(...)'.

> > Commit 568f196756ad ("bpf: check that BPF programs run with preemption disabled")

> > highlighted the issue.

> >

> > Suggested-by: Arnd Bergmann <arnd@arndb.de>

> > Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

>

> Hmm, wrong commit description?


urgh, you are correct. I'm sorry.
Sending a v2 shortly.

> Below code is not related to seccomp

> but rather BPF test suite. Could you fix it up and resubmit? Rest

> looks okay to me.

>

> > ---

> >  lib/test_bpf.c | 2 ++

> >  1 file changed, 2 insertions(+)

> >

> > diff --git a/lib/test_bpf.c b/lib/test_bpf.c

> > index f3e570722a7e..0845f635f404 100644

> > --- a/lib/test_bpf.c

> > +++ b/lib/test_bpf.c

> > @@ -6668,12 +6668,14 @@ static int __run_one(const struct bpf_prog *fp, const void *data,

> >       u64 start, finish;

> >       int ret = 0, i;

> >

> > +     preempt_disable();

> >       start = ktime_get_ns();

> >

> >       for (i = 0; i < runs; i++)

> >               ret = BPF_PROG_RUN(fp, data);

> >

> >       finish = ktime_get_ns();

> > +     preempt_enable();

> >

> >       *duration = finish - start;

> >       do_div(*duration, runs);

> >

>

Patch

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index f3e570722a7e..0845f635f404 100644
--- a/lib/test_bpf.c
+++ b/lib/test_bpf.c
@@ -6668,12 +6668,14 @@  static int __run_one(const struct bpf_prog *fp, const void *data,
 	u64 start, finish;
 	int ret = 0, i;
 
+	preempt_disable();
 	start = ktime_get_ns();
 
 	for (i = 0; i < runs; i++)
 		ret = BPF_PROG_RUN(fp, data);
 
 	finish = ktime_get_ns();
+	preempt_enable();
 
 	*duration = finish - start;
 	do_div(*duration, runs);