[PATCH] kmsan: test: check vmalloc return value before use

[Liu Jing]

In test_init_vmalloc(), the return value of vmalloc() is used directly
without a NULL check. If vmalloc() fails under memory pressure, the
subsequent buf[0] = 1 and memset() calls will dereference a NULL
pointer and cause a kernel panic.

Add a NULL check immediately after vmalloc() and skip the test if
allocation fails.

Signed-off-by: Liu Jing <liu...@cmss.chinamobile.com>
---
mm/kmsan/kmsan_test.c | 6 ++++++
1 file changed, 6 insertion(+), 0 deletion(-)

--- a/mm/kmsan/kmsan_test.c
+++ b/mm/kmsan/kmsan_test.c
@@ -352,6 +352,12 @@

kunit_info(test, "vmalloc buffer can be initialized (no reports)\n");
buf = vmalloc(PAGE_SIZE * npages);
+
+ if (!buf) {
+ kunit_skip(test, "vmalloc failed, skipping test\n");
+ return;
+ }
+
buf[0] = 1;
memset(buf, 0xfe, PAGE_SIZE * npages);
USE(buf[0]);

--
2.43.0

[Alexander Potapenko]

On Wed, Sep 2, 2026 at 10:56 AM Liu Jing <liu...@cmss.chinamobile.com> wrote:
>
> In test_init_vmalloc(), the return value of vmalloc() is used directly
> without a NULL check. If vmalloc() fails under memory pressure, the
> subsequent buf[0] = 1 and memset() calls will dereference a NULL
> pointer and cause a kernel panic.

Out of curiosity, have you actually observed vmalloc() failing under
memory pressure during this test?

> Add a NULL check immediately after vmalloc() and skip the test if
> allocation fails.
>
> Signed-off-by: Liu Jing <liu...@cmss.chinamobile.com>
> ---
> mm/kmsan/kmsan_test.c | 6 ++++++
> 1 file changed, 6 insertion(+), 0 deletion(-)
>
> --- a/mm/kmsan/kmsan_test.c
> +++ b/mm/kmsan/kmsan_test.c
> @@ -352,6 +352,12 @@
>
> kunit_info(test, "vmalloc buffer can be initialized (no reports)\n");
> buf = vmalloc(PAGE_SIZE * npages);
> +
> + if (!buf) {
> + kunit_skip(test, "vmalloc failed, skipping test\n");
> + return;
> + }

While at it, can you add similar checks to other allocation sites in this file?
The problem is not specific to vmalloc()

> buf[0] = 1;
> memset(buf, 0xfe, PAGE_SIZE * npages);
> USE(buf[0]);
>
> --
> 2.43.0
>
>

--
Alexander Potapenko
Software Engineer

Google Germany GmbH
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