linux-kernel - Re: [PATCH v2] mm/vmalloc: fix vmalloc which may return null if called with __GFP

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Message-ID: <Zj3_T_lFU6WGUXHt@pc636>
Date: Fri, 10 May 2024 13:04:47 +0200
From: Uladzislau Rezki <urezki@...il.com>
To: hailong.liu@...o.com
Cc: akpm@...ux-foundation.org, urezki@...il.com, hch@...radead.org,
	lstoakes@...il.com, 21cnbao@...il.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, xiang@...nel.org, chao@...nel.org,
	mhocko@...e.com, stable@...r.kernel.org,
	Oven <liyangouwen1@...o.com>
Subject: Re: [PATCH v2] mm/vmalloc: fix vmalloc which may return null if
 called with __GFP_NOFAIL

On Fri, May 10, 2024 at 06:01:31PM +0800, hailong.liu@...o.com wrote:
> From: "Hailong.Liu" <hailong.liu@...o.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 follows:
> 
> process-a
> __vmalloc_node_range(GFP_KERNEL | __GFP_NOFAIL)
>     __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.
> 
> Fixes: 9376130c390a ("mm/vmalloc: add support for __GFP_NOFAIL")
> Cc: <stable@...r.kernel.org>
> Acked-by: Michal Hocko <mhocko@...e.com>
> Suggested-by: Barry Song <21cnbao@...il.com>
> Reported-by: Oven <liyangouwen1@...o.com>
> Signed-off-by: Hailong.Liu <hailong.liu@...o.com>
> ---
>  mm/vmalloc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 125427cbdb87..109272b8ee2e 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3492,7 +3492,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>  {
>  	unsigned int nr_allocated = 0;
>  	gfp_t alloc_gfp = gfp;
> -	bool nofail = false;
> +	bool nofail = gfp & __GFP_NOFAIL;
>  	struct page *page;
>  	int i;
> 
> @@ -3549,12 +3549,11 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>  		 * and compaction etc.
>  		 */
>  		alloc_gfp &= ~__GFP_NOFAIL;
> -		nofail = true;
>  	}
> 
>  	/* High-order pages or fallback path if "bulk" fails. */
>  	while (nr_allocated < nr_pages) {
> -		if (fatal_signal_pending(current))
> +		if (!nofail && fatal_signal_pending(current))
>  			break;
> 
>  		if (nid == NUMA_NO_NODE)
> ---
> Changes since RFC v1 [1]:
> - Remove RFC tag
> - Add fixes, per Michal
> - Use nofail instead of gfp & __GFP_NOFAIL, per Barry & Michal
> - Modify commit log, per Barry
> 
> [1] https://lore.kernel.org/all/20240508125808.28882-1-hailong.liu@oppo.com/
> 
> This issue occurred during OPLUS KASAN TEST. Below is part of the log
> -> oom-killer sends signal to process
> [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
> 
Makes sense to me:

Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>

--
Uladzislau Rezki