Re: [RFC PATCH] mm/vmalloc: fix vmalloc which may return null if called with __GFP_NOFAIL

[Gao Xiang <hsiangkao@linux.alibaba.com>]

+Cc Michal,

On 2024/5/8 20:58, hailong.liu@oppo.com wrote:
> From: "Hailong.Liu" <hailong.liu@oppo.com>
> 
> Commit a421ef303008 ("mm: allow !GFP_KERNEL allocations for kvmalloc")
> includes support for __GFP_NOFAIL, but it presents a conflict with
> commit dd544141b9eb ("vmalloc: back off when the current task is
> OOM-killed"). A possible scenario is as belows:
> 
> process-a
> kvcalloc(n, m, GFP_KERNEL | __GFP_NOFAIL)
>      __vmalloc_node_range()
> 	__vmalloc_area_node()
> 	    vm_area_alloc_pages()
>              --> oom-killer send SIGKILL to process-a
>              if (fatal_signal_pending(current)) break;
> --> return NULL;
> 
> to fix this, do not check fatal_signal_pending() in vm_area_alloc_pages()
> if __GFP_NOFAIL set.
> 
> Reported-by: Oven <liyangouwen1@oppo.com>
> Signed-off-by: Hailong.Liu <hailong.liu@oppo.com>

Why taging this as RFC here?  It seems a corner-case fix of
commit a421ef303008

Thanks,
Gao Xiang

> ---
>   mm/vmalloc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 6641be0ca80b..2f359d08bf8d 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3560,7 +3560,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> 
>   	/* High-order pages or fallback path if "bulk" fails. */
>   	while (nr_allocated < nr_pages) {
> -		if (fatal_signal_pending(current))
> +		if (!(gfp & __GFP_NOFAIL) && fatal_signal_pending(current))
>   			break;
> 
>   		if (nid == NUMA_NO_NODE)
> ---
> This issue occurred during OPLUS KASAN test. Below is part of the log
> 
> -> send signal
> [65731.222840] [ T1308] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=/,mems_allowed=0,global_oom,task_memcg=/apps/uid_10198,task=gs.intelligence,pid=32454,uid=10198
> 
> [65731.259685] [T32454] Call trace:
> [65731.259698] [T32454]  dump_backtrace+0xf4/0x118
> [65731.259734] [T32454]  show_stack+0x18/0x24
> [65731.259756] [T32454]  dump_stack_lvl+0x60/0x7c
> [65731.259781] [T32454]  dump_stack+0x18/0x38
> [65731.259800] [T32454]  mrdump_common_die+0x250/0x39c [mrdump]
> [65731.259936] [T32454]  ipanic_die+0x20/0x34 [mrdump]
> [65731.260019] [T32454]  atomic_notifier_call_chain+0xb4/0xfc
> [65731.260047] [T32454]  notify_die+0x114/0x198
> [65731.260073] [T32454]  die+0xf4/0x5b4
> [65731.260098] [T32454]  die_kernel_fault+0x80/0x98
> [65731.260124] [T32454]  __do_kernel_fault+0x160/0x2a8
> [65731.260146] [T32454]  do_bad_area+0x68/0x148
> [65731.260174] [T32454]  do_mem_abort+0x151c/0x1b34
> [65731.260204] [T32454]  el1_abort+0x3c/0x5c
> [65731.260227] [T32454]  el1h_64_sync_handler+0x54/0x90
> [65731.260248] [T32454]  el1h_64_sync+0x68/0x6c
> [65731.260269] [T32454]  z_erofs_decompress_queue+0x7f0/0x2258
> --> be->decompressed_pages = kvcalloc(be->nr_pages, sizeof(struct page *), GFP_KERNEL | __GFP_NOFAIL);
> 	kernel panic by NULL pointer dereference.
> 	erofs assume kvmalloc with __GFP_NOFAIL never return NULL.
> 
> [65731.260293] [T32454]  z_erofs_runqueue+0xf30/0x104c
> [65731.260314] [T32454]  z_erofs_readahead+0x4f0/0x968
> [65731.260339] [T32454]  read_pages+0x170/0xadc
> [65731.260364] [T32454]  page_cache_ra_unbounded+0x874/0xf30
> [65731.260388] [T32454]  page_cache_ra_order+0x24c/0x714
> [65731.260411] [T32454]  filemap_fault+0xbf0/0x1a74
> [65731.260437] [T32454]  __do_fault+0xd0/0x33c
> [65731.260462] [T32454]  handle_mm_fault+0xf74/0x3fe0
> [65731.260486] [T32454]  do_mem_abort+0x54c/0x1b34
> [65731.260509] [T32454]  el0_da+0x44/0x94
> [65731.260531] [T32454]  el0t_64_sync_handler+0x98/0xb4
> [65731.260553] [T32454]  el0t_64_sync+0x198/0x19c
> 
> --
> 2.34.1