From 9f6c6ad161f1af37548a6b80fb15710998ccfd1e Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <lstoakes@gmail.com>
Date: Wed, 24 May 2023 09:24:24 +0100
Subject: [PATCH] lib/test_vmalloc.c: avoid garbage in page array
It turns out that alloc_pages_bulk_array() does not treat the page_array
parameter as an output parameter, but rather reads the array and skips any
entries that have already been allocated.
This is somewhat unexpected and breaks this test, as we allocate the pages
array uninitialised on the assumption it will be overwritten.
As a result, the test was referencing uninitialised data and causing the
PFN to not be valid and thus a WARN_ON() followed by a null pointer deref
and panic.
In addition, this is an array of pointers not of struct page objects, so we
need only allocate an array with elements of pointer size.
We solve both problems by simply using kcalloc() and referencing
sizeof(struct page *) rather than sizeof(struct page).
Link: https://lkml.kernel.org/r/20230524082424.10022-1-lstoakes@gmail.com
Fixes: 869cb29a61a1 ("lib/test_vmalloc.c: add vm_map_ram()/vm_unmap_ram() test case")
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
lib/test_vmalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c
index 9dd9745d365f7..3718d9886407d 100644
--- a/lib/test_vmalloc.c
+++ b/lib/test_vmalloc.c
@@ -369,7 +369,7 @@ vm_map_ram_test(void)
int i;
map_nr_pages = nr_pages > 0 ? nr_pages:1;
- pages = kmalloc(map_nr_pages * sizeof(struct page), GFP_KERNEL);
+ pages = kcalloc(map_nr_pages, sizeof(struct page *), GFP_KERNEL);
if (!pages)
return -1;
--
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