* [PATCH nf,v2] netfilter: nf_tables: disable bh to update per-cpu rnd_state
@ 2022-05-18 16:00 Pablo Neira Ayuso
2022-05-18 16:46 ` Florian Westphal
0 siblings, 1 reply; 3+ messages in thread
From: Pablo Neira Ayuso @ 2022-05-18 16:00 UTC (permalink / raw)
To: netfilter-devel; +Cc: fw, fasnacht
bh might occur while updating per-cpu rnd_state from user context,
ie. local_out path.
[233241.951068] BUG: using smp_processor_id() in preemptible [00000000] code: nginx/2725
[233241.951220] caller is nft_ng_random_eval+0x24/0x54 [nft_numgen]
[233241.951225] CPU: 2 PID: 2725 Comm: nginx Tainted: G OE 5.16.0-0.bpo.4-amd64 #1 Debian 5.16.12-1~bpo11+1
[233241.951227] Hardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021
[233241.951228] Call Trace:
[233241.951231] <TASK>
[233241.951233] dump_stack_lvl+0x48/0x5e
[233241.951236] check_preemption_disabled+0xde/0xe0
[233241.951239] nft_ng_random_eval+0x24/0x54 [nft_numgen]
Fixes: 6b2faee0ca91 ("netfilter: nft_meta: place prandom handling in a helper")
Fixes: 978d8f9055c3 ("netfilter: nft_numgen: add map lookups for numgen random operations")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
v2: disable/enable bh
@Florian: your rand meta support is missing {disable,enable}_local_bh()
net/netfilter/nft_meta.c | 10 ++++++++--
net/netfilter/nft_numgen.c | 11 ++++++++---
2 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
index ac4859241e17..30aded940f91 100644
--- a/net/netfilter/nft_meta.c
+++ b/net/netfilter/nft_meta.c
@@ -273,9 +273,15 @@ static bool nft_meta_get_eval_ifname(enum nft_meta_keys key, u32 *dest,
static noinline u32 nft_prandom_u32(void)
{
- struct rnd_state *state = this_cpu_ptr(&nft_prandom_state);
+ struct rnd_state *state;
+ u32 ret;
- return prandom_u32_state(state);
+ local_bh_disable();
+ state = this_cpu_ptr(&nft_prandom_state);
+ ret = prandom_u32_state(state);
+ local_bh_enable();
+
+ return ret;
}
#ifdef CONFIG_IP_ROUTE_CLASSID
diff --git a/net/netfilter/nft_numgen.c b/net/netfilter/nft_numgen.c
index 81b40c663d86..911589ad3837 100644
--- a/net/netfilter/nft_numgen.c
+++ b/net/netfilter/nft_numgen.c
@@ -137,10 +137,15 @@ struct nft_ng_random {
static u32 nft_ng_random_gen(struct nft_ng_random *priv)
{
- struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
+ struct rnd_state *state;
+ u32 ret;
- return reciprocal_scale(prandom_u32_state(state), priv->modulus) +
- priv->offset;
+ local_bh_disable();
+ state = this_cpu_ptr(&nft_numgen_prandom_state);
+ ret = prandom_u32_state(state);
+ local_bh_enable();
+
+ return reciprocal_scale(ret, priv->modulus) + priv->offset;
}
static void nft_ng_random_eval(const struct nft_expr *expr,
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH nf,v2] netfilter: nf_tables: disable bh to update per-cpu rnd_state
2022-05-18 16:00 [PATCH nf,v2] netfilter: nf_tables: disable bh to update per-cpu rnd_state Pablo Neira Ayuso
@ 2022-05-18 16:46 ` Florian Westphal
2022-05-18 17:51 ` Pablo Neira Ayuso
0 siblings, 1 reply; 3+ messages in thread
From: Florian Westphal @ 2022-05-18 16:46 UTC (permalink / raw)
To: Pablo Neira Ayuso; +Cc: netfilter-devel, fw, fasnacht
Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> bh might occur while updating per-cpu rnd_state from user context,
> ie. local_out path.
>
> [233241.951068] BUG: using smp_processor_id() in preemptible [00000000] code: nginx/2725
> [233241.951220] caller is nft_ng_random_eval+0x24/0x54 [nft_numgen]
> [233241.951225] CPU: 2 PID: 2725 Comm: nginx Tainted: G OE 5.16.0-0.bpo.4-amd64 #1 Debian 5.16.12-1~bpo11+1
> [233241.951227] Hardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021
> [233241.951228] Call Trace:
> [233241.951231] <TASK>
> [233241.951233] dump_stack_lvl+0x48/0x5e
> [233241.951236] check_preemption_disabled+0xde/0xe0
> [233241.951239] nft_ng_random_eval+0x24/0x54 [nft_numgen]
>
> Fixes: 6b2faee0ca91 ("netfilter: nft_meta: place prandom handling in a helper")
> Fixes: 978d8f9055c3 ("netfilter: nft_numgen: add map lookups for numgen random operations")
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> ---
> v2: disable/enable bh
> @Florian: your rand meta support is missing {disable,enable}_local_bh()
I wonder if its better to just switch to get_random_u32() instead of prandom.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH nf,v2] netfilter: nf_tables: disable bh to update per-cpu rnd_state
2022-05-18 16:46 ` Florian Westphal
@ 2022-05-18 17:51 ` Pablo Neira Ayuso
0 siblings, 0 replies; 3+ messages in thread
From: Pablo Neira Ayuso @ 2022-05-18 17:51 UTC (permalink / raw)
To: Florian Westphal; +Cc: netfilter-devel, fasnacht
On Wed, May 18, 2022 at 06:46:21PM +0200, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > bh might occur while updating per-cpu rnd_state from user context,
> > ie. local_out path.
> >
> > [233241.951068] BUG: using smp_processor_id() in preemptible [00000000] code: nginx/2725
> > [233241.951220] caller is nft_ng_random_eval+0x24/0x54 [nft_numgen]
> > [233241.951225] CPU: 2 PID: 2725 Comm: nginx Tainted: G OE 5.16.0-0.bpo.4-amd64 #1 Debian 5.16.12-1~bpo11+1
> > [233241.951227] Hardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021
> > [233241.951228] Call Trace:
> > [233241.951231] <TASK>
> > [233241.951233] dump_stack_lvl+0x48/0x5e
> > [233241.951236] check_preemption_disabled+0xde/0xe0
> > [233241.951239] nft_ng_random_eval+0x24/0x54 [nft_numgen]
> >
> > Fixes: 6b2faee0ca91 ("netfilter: nft_meta: place prandom handling in a helper")
> > Fixes: 978d8f9055c3 ("netfilter: nft_numgen: add map lookups for numgen random operations")
> > Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> > ---
> > v2: disable/enable bh
> > @Florian: your rand meta support is missing {disable,enable}_local_bh()
>
> I wonder if its better to just switch to get_random_u32() instead of prandom.
Feel free to pick if you would like to send a v3.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-05-18 17:51 UTC | newest]
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2022-05-18 16:00 [PATCH nf,v2] netfilter: nf_tables: disable bh to update per-cpu rnd_state Pablo Neira Ayuso
2022-05-18 16:46 ` Florian Westphal
2022-05-18 17:51 ` Pablo Neira Ayuso
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