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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>,
	Hailong.Liu <hailong.liu@oppo.com>
Subject: [RFC PATCH v2] mm/vmalloc: fix return value of vb_alloc if size is 0.
Date: Fri, 19 Apr 2024 18:16:43 +0800
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From: "Hailong.Liu" <hailong.liu@oppo.com>

vm_map_ram check return value of vb_alloc by IS_ERR. if
vm_map_ram(page, 0, 0) , vb_alloc(0, GFP_KERNEL) would return NULL
which cause kernel panic by vmap_pages_range_noflush。fix this by
return ERR_PTR(-EINVAL) if size is 0.

Signed-off-by: Hailong.Liu <hailong.liu@oppo.com>
---
Changes since v1 [1]:
- Return ERR_PTR(-EINVAL) or not check IS_ERR_OR_NULL

BTW,  Barry suggests me that if count is 0, return directly, in my
opinion, change return value is more resonable.

[1] https://lore.kernel.org/all/84d7cd03-1cf8-401a-8edf-2524db0bd6d5@oppo.com/

 mm/vmalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a3fedb3ee0db..c430a999805b 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2173,7 +2173,7 @@ static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
 		 * get_order(0) returns funny result. Just warn and terminate
 		 * early.
 		 */
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	}
 	order = get_order(size);

--
2.34.1