* [PATCH] bpf: remove unnecessary condition in bpf_check()
@ 2018-07-09 11:48 Tobias Tefke
2018-07-09 23:01 ` Alexei Starovoitov
0 siblings, 1 reply; 2+ messages in thread
From: Tobias Tefke @ 2018-07-09 11:48 UTC (permalink / raw)
To: tobias.tefke, ast, daniel; +Cc: netdev, linux-kernel
In the label skip_full_check the function sanitize_dead_code()
is being called if the return value equals zero.
After that call there is another condition checking
if the return value equals zero.
If this condition evaluates to true,
check_max_stack_depth() is being called.
However, sanitize_dead_code() has no return value.
Therefore the return value of bpf_check() is still the same
and the condition can be removed.
Signed-off-by: Tobias Tefke <tobias.tefke@tutanota.com>
---
kernel/bpf/verifier.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9e2bf834f13a..b022d0a85427 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5935,11 +5935,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
while (!pop_stack(env, NULL, NULL));
free_states(env);
- if (ret == 0)
+ if (ret == 0) {
sanitize_dead_code(env);
-
- if (ret == 0)
ret = check_max_stack_depth(env);
+ }
if (ret == 0)
/* program is valid, convert *(u32*)(ctx + off) accesses */
--
2.18.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] bpf: remove unnecessary condition in bpf_check()
2018-07-09 11:48 [PATCH] bpf: remove unnecessary condition in bpf_check() Tobias Tefke
@ 2018-07-09 23:01 ` Alexei Starovoitov
0 siblings, 0 replies; 2+ messages in thread
From: Alexei Starovoitov @ 2018-07-09 23:01 UTC (permalink / raw)
To: Tobias Tefke; +Cc: tobias.tefke, ast, daniel, netdev, linux-kernel
On Mon, Jul 09, 2018 at 01:48:37PM +0200, Tobias Tefke wrote:
> In the label skip_full_check the function sanitize_dead_code()
> is being called if the return value equals zero.
> After that call there is another condition checking
> if the return value equals zero.
> If this condition evaluates to true,
> check_max_stack_depth() is being called.
> However, sanitize_dead_code() has no return value.
> Therefore the return value of bpf_check() is still the same
> and the condition can be removed.
>
> Signed-off-by: Tobias Tefke <tobias.tefke@tutanota.com>
> ---
> kernel/bpf/verifier.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 9e2bf834f13a..b022d0a85427 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -5935,11 +5935,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
> while (!pop_stack(env, NULL, NULL));
> free_states(env);
>
> - if (ret == 0)
> + if (ret == 0) {
> sanitize_dead_code(env);
> -
> - if (ret == 0)
> ret = check_max_stack_depth(env);
> + }
Technically the patch is correct, but I think it would make
the code harder to read. I prefer to keep it as-is.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2018-07-09 11:48 [PATCH] bpf: remove unnecessary condition in bpf_check() Tobias Tefke
2018-07-09 23:01 ` Alexei Starovoitov
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