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From: <hailong.liu@oppo.com>
To: <akpm@linux-foundation.org>
CC: <urezki@gmail.com>, <hch@infradead.org>, <lstoakes@gmail.com>,
	<21cnbao@gmail.com>, <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
	<xiang@kernel.org>, <chao@kernel.org>, Hailong.Liu <hailong.liu@oppo.com>,
	Oven <liyangouwen1@oppo.com>
Subject: [RFC PATCH] mm/vmalloc: fix vmalloc which may return null if called with __GFP_NOFAIL
Date: Wed, 8 May 2024 20:58:08 +0800
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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>
---
 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