On Wed, May 18, 2022 at 06:46:21PM +0200, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > ---
> > 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.
