Subject: Re: [PATCH mm] mm: fix BUG with kvzalloc+GFP_ATOMIC

From: Florian Westphal <[email-masked]>
Date: Fri, 23 Sep 2022 15:35:12 +0200

Michal Hocko <[email-masked]> wrote:
> On Fri 23-09-22 12:38:58, Florian Westphal wrote:
> > Martin Zaharinov reports BUG() in mm land for 5.19.10 kernel:
> >  kernel BUG at mm/vmalloc.c:2437!
> >  invalid opcode: 0000 [#1] SMP
> >  CPU: 28 PID: 0 Comm: swapper/28 Tainted: G        W  O      5.19.9 #1
> >  [..]
> >  RIP: 0010:__get_vm_area_node+0x120/0x130
> >   __vmalloc_node_range+0x96/0x1e0
> >   kvmalloc_node+0x92/0xb0
> >   bucket_table_alloc.isra.0+0x47/0x140
> >   rhashtable_try_insert+0x3a4/0x440
> >   rhashtable_insert_slow+0x1b/0x30
> >  [..]
> > 
> > bucket_table_alloc uses kvzallocGPF_ATOMIC).  If kmalloc fails, this now
> > falls through to vmalloc and hits code paths that assume GFP_KERNEL.
> > 
> > Revert the problematic change and stay with slab allocator.
> 
> Why don't you simply fix the caller?

Uh, not following?

kvzalloc(GFP_ATOMIC) was perfectly fine, is this illegal again?

I can revert 93f976b5190df32793908d49165f78e67fcb66cf instead
but that change is from 2018.