On Mon 26-09-22 10:31:39, 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 kvzalloc(GPF_ATOMIC). If kmalloc fails, this now
> falls through to vmalloc and hits code paths that assume GFP_KERNEL.
>
> I sent a patch to restore GFP_ATOMIC support in kvmalloc but mm
> maintainers rejected it.
>
> This patch is partial revert of
> commit 93f976b5190d ("lib/rhashtable: simplify bucket_table_alloc()"),
> to avoid kvmalloc for ATOMIC case.
>
> As kvmalloc doesn't warn when used with ATOMIC, kernel will only crash
> once vmalloc fallback occurs, so we may see more crashes in other areas
> in the future.
>
> Most other callers seem ok but kvm_mmu_topup_memory_cache looks like it
> might be affected by the same breakage, so Cc kvm@.
>
> Reported-by: Martin Zaharinov <micron10@xxxxxxxxx>
> Fixes: a421ef303008 ("mm: allow !GFP_KERNEL allocations for kvmalloc")
> Link: https://lore.kernel.org/linux-mm/Yy3MS2uhSgjF47dy@pc636/T/#t
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx
> Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Please continue in the original email thread until we sort out the most
reasonable solution for this.
--
Michal Hocko
SUSE Labs
