Re: [PATCH v2 mm] mm: fix BUG splat with kvmalloc + GFP_ATOMIC

Michal Hocko
2022-09-26T15:23:39Z

On Mon 26-09-22 17:16:50, Florian Westphal wrote:
> Martin Zaharinov reports BUG with 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 kvzalloc(GPF_ATOMIC). If kmalloc fails, this now
> falls through to vmalloc and hits code paths that assume GFP_KERNEL.
>
> Reported-by: Martin Zaharinov <micron10@gmail.com>
> Fixes: a421ef303008 ("mm: allow !GFP_KERNEL allocations for kvmalloc")
> Suggested-by: Michal Hocko <mhocko@suse.com>
> Link: https://lore.kernel.org/linux-mm/Yy3MS2uhSgjF47dy@pc636/T/#t
> Signed-off-by: Florian Westphal <fw@strlen.de>

Maybe we can extend this to GFP_NOWAIT capable vmalloc call but I am not
sure this exists or whether this is something vmalloc maintainers want
to commit to.

This is a clear and trivial fixup of the above commit. I would add this
to the stable tree as well.

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
> mm/util.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/mm/util.c b/mm/util.c
> index c9439c66d8cf..346e40177bc6 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -619,6 +619,10 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
> if (ret || size <= PAGE_SIZE)
> return ret;
>
> + /* non-sleeping allocations are not supported by vmalloc */
> + if (!gfpflags_allow_blocking(flags))
> + return NULL;
> +
> /* Don't even allow crazy sizes */
> if (unlikely(size > INT_MAX)) {
> WARN_ON_ONCE(!(flags & __GFP_NOWARN));
> --
> 2.35.1

--
Michal Hocko
SUSE Labs