* [PATCH v2 bpf] bpf: Fix a data-race around bpf_jit_limit.
@ 2022-08-23 18:12 Kuniyuki Iwashima
2022-08-23 21:20 ` Daniel Borkmann
0 siblings, 1 reply; 3+ messages in thread
From: Kuniyuki Iwashima @ 2022-08-23 18:12 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko
Cc: Kuniyuki Iwashima, Kuniyuki Iwashima, bpf, netdev
While reading bpf_jit_limit, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.
Fixes: ede95a63b5e8 ("bpf: add bpf_jit_limit knob to restrict unpriv allocations")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
v2:
* Drop other 3 patches (No change for this patch)
v1: https://lore.kernel.org/bpf/20220818042339.82992-1-kuniyu@amazon.com/
---
kernel/bpf/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index c1e10d088dbb..3d9eb3ae334c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -971,7 +971,7 @@ pure_initcall(bpf_jit_charge_init);
int bpf_jit_charge_modmem(u32 size)
{
- if (atomic_long_add_return(size, &bpf_jit_current) > bpf_jit_limit) {
+ if (atomic_long_add_return(size, &bpf_jit_current) > READ_ONCE(bpf_jit_limit)) {
if (!bpf_capable()) {
atomic_long_sub(size, &bpf_jit_current);
return -EPERM;
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2 bpf] bpf: Fix a data-race around bpf_jit_limit.
2022-08-23 18:12 [PATCH v2 bpf] bpf: Fix a data-race around bpf_jit_limit Kuniyuki Iwashima
@ 2022-08-23 21:20 ` Daniel Borkmann
2022-08-23 21:51 ` Kuniyuki Iwashima
0 siblings, 1 reply; 3+ messages in thread
From: Daniel Borkmann @ 2022-08-23 21:20 UTC (permalink / raw)
To: Kuniyuki Iwashima, Alexei Starovoitov, Andrii Nakryiko
Cc: Kuniyuki Iwashima, bpf, netdev
On 8/23/22 8:12 PM, Kuniyuki Iwashima wrote:
> While reading bpf_jit_limit, it can be changed concurrently.
> Thus, we need to add READ_ONCE() to its reader.
For sake of a better/clearer commit message, please also provide data about the
WRITE_ONCE() pairing that this READ_ONCE() targets. This seems to be the case in
__do_proc_doulongvec_minmax() as far as I can see. For your 2nd sentence above
please also include load-tearing as main motivation for your fix.
> Fixes: ede95a63b5e8 ("bpf: add bpf_jit_limit knob to restrict unpriv allocations")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---
> v2:
> * Drop other 3 patches (No change for this patch)
>
> v1: https://lore.kernel.org/bpf/20220818042339.82992-1-kuniyu@amazon.com/
> ---
> kernel/bpf/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index c1e10d088dbb..3d9eb3ae334c 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -971,7 +971,7 @@ pure_initcall(bpf_jit_charge_init);
>
> int bpf_jit_charge_modmem(u32 size)
> {
> - if (atomic_long_add_return(size, &bpf_jit_current) > bpf_jit_limit) {
> + if (atomic_long_add_return(size, &bpf_jit_current) > READ_ONCE(bpf_jit_limit)) {
> if (!bpf_capable()) {
> atomic_long_sub(size, &bpf_jit_current);
> return -EPERM;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2 bpf] bpf: Fix a data-race around bpf_jit_limit.
2022-08-23 21:20 ` Daniel Borkmann
@ 2022-08-23 21:51 ` Kuniyuki Iwashima
0 siblings, 0 replies; 3+ messages in thread
From: Kuniyuki Iwashima @ 2022-08-23 21:51 UTC (permalink / raw)
To: daniel; +Cc: andrii, ast, bpf, kuni1840, kuniyu, netdev
From: Daniel Borkmann <daniel@iogearbox.net>
Date: Tue, 23 Aug 2022 23:20:29 +0200
> On 8/23/22 8:12 PM, Kuniyuki Iwashima wrote:
> > While reading bpf_jit_limit, it can be changed concurrently.
> > Thus, we need to add READ_ONCE() to its reader.
>
> For sake of a better/clearer commit message, please also provide data about the
> WRITE_ONCE() pairing that this READ_ONCE() targets. This seems to be the case in
> __do_proc_doulongvec_minmax() as far as I can see. For your 2nd sentence above
> please also include load-tearing as main motivation for your fix.
I'll add better description.
Thank you!
>
> > Fixes: ede95a63b5e8 ("bpf: add bpf_jit_limit knob to restrict unpriv allocations")
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> > ---
> > v2:
> > * Drop other 3 patches (No change for this patch)
> >
> > v1: https://lore.kernel.org/bpf/20220818042339.82992-1-kuniyu@amazon.com/
> > ---
> > kernel/bpf/core.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> > index c1e10d088dbb..3d9eb3ae334c 100644
> > --- a/kernel/bpf/core.c
> > +++ b/kernel/bpf/core.c
> > @@ -971,7 +971,7 @@ pure_initcall(bpf_jit_charge_init);
> >
> > int bpf_jit_charge_modmem(u32 size)
> > {
> > - if (atomic_long_add_return(size, &bpf_jit_current) > bpf_jit_limit) {
> > + if (atomic_long_add_return(size, &bpf_jit_current) > READ_ONCE(bpf_jit_limit)) {
> > if (!bpf_capable()) {
> > atomic_long_sub(size, &bpf_jit_current);
> > return -EPERM;
> >
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-08-23 18:12 [PATCH v2 bpf] bpf: Fix a data-race around bpf_jit_limit Kuniyuki Iwashima
2022-08-23 21:20 ` Daniel Borkmann
2022-08-23 21:51 ` Kuniyuki Iwashima
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