Re: [PATCH bpf] bpf: disable and restore preemption in __BPF_PROG_RUN_ARRAY

[Daniel Borkmann]

On 04/23/2018 07:09 PM, Roman Gushchin wrote:
> Running bpf programs requires disabled preemption,
> however at least some* of the BPF_PROG_RUN_ARRAY users
> do not follow this rule.
> 
> To fix this bug, and also to make it not happen in the future,
> let's add explicit preemption disabling/re-enabling
> to the __BPF_PROG_RUN_ARRAY code.
> 
> * for example:
>  [   17.624472] RIP: 0010:__cgroup_bpf_run_filter_sk+0x1c4/0x1d0
>  ...
>  [   17.640890]  inet6_create+0x3eb/0x520
>  [   17.641405]  __sock_create+0x242/0x340
>  [   17.641939]  __sys_socket+0x57/0xe0
>  [   17.642370]  ? trace_hardirqs_off_thunk+0x1a/0x1c
>  [   17.642944]  SyS_socket+0xa/0x10
>  [   17.643357]  do_syscall_64+0x79/0x220
>  [   17.643879]  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> 
> Signed-off-by: Roman Gushchin 
> Cc: Alexei Starovoitov 
> Cc: Daniel Borkmann 

Applied to bpf, thanks Roman.

Re: [PATCH bpf] bpf: disable and restore preemption in __BPF_PROG_RUN_ARRAY

[Alexei Starovoitov]

On Mon, Apr 23, 2018 at 06:09:21PM +0100, Roman Gushchin wrote:
> Running bpf programs requires disabled preemption,
> however at least some* of the BPF_PROG_RUN_ARRAY users
> do not follow this rule.
> 
> To fix this bug, and also to make it not happen in the future,
> let's add explicit preemption disabling/re-enabling
> to the __BPF_PROG_RUN_ARRAY code.
> 
> * for example:
>  [   17.624472] RIP: 0010:__cgroup_bpf_run_filter_sk+0x1c4/0x1d0
>  ...
>  [   17.640890]  inet6_create+0x3eb/0x520
>  [   17.641405]  __sock_create+0x242/0x340
>  [   17.641939]  __sys_socket+0x57/0xe0
>  [   17.642370]  ? trace_hardirqs_off_thunk+0x1a/0x1c
>  [   17.642944]  SyS_socket+0xa/0x10
>  [   17.643357]  do_syscall_64+0x79/0x220
>  [   17.643879]  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> 
> Signed-off-by: Roman Gushchin 
> Cc: Alexei Starovoitov 
> Cc: Daniel Borkmann 

Acked-by: Alexei Starovoitov 

[PATCH bpf] bpf: disable and restore preemption in __BPF_PROG_RUN_ARRAY

[Roman Gushchin]

Running bpf programs requires disabled preemption,
however at least some* of the BPF_PROG_RUN_ARRAY users
do not follow this rule.

To fix this bug, and also to make it not happen in the future,
let's add explicit preemption disabling/re-enabling
to the __BPF_PROG_RUN_ARRAY code.

* for example:
 [   17.624472] RIP: 0010:__cgroup_bpf_run_filter_sk+0x1c4/0x1d0
 ...
 [   17.640890]  inet6_create+0x3eb/0x520
 [   17.641405]  __sock_create+0x242/0x340
 [   17.641939]  __sys_socket+0x57/0xe0
 [   17.642370]  ? trace_hardirqs_off_thunk+0x1a/0x1c
 [   17.642944]  SyS_socket+0xa/0x10
 [   17.643357]  do_syscall_64+0x79/0x220
 [   17.643879]  entry_SYSCALL_64_after_hwframe+0x42/0xb7

Signed-off-by: Roman Gushchin 
Cc: Alexei Starovoitov 
Cc: Daniel Borkmann 
---
 include/linux/bpf.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 486e65e3db26..dc586cc64bc2 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -351,6 +351,7 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu 
*old_array,
struct bpf_prog **_prog, *__prog;   \
struct bpf_prog_array *_array;  \
u32 _ret = 1;   \
+   preempt_disable();  \
rcu_read_lock();\
_array = rcu_dereference(array);\
if (unlikely(check_non_null && !_array))\
@@ -362,6 +363,7 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu 
*old_array,
}   \
 _out:  \
rcu_read_unlock();  \
+   preempt_enable_no_resched();\
_ret;   \
 })
 
-- 
2.14.3