[PATCH 5.17 004/298] lkdtm/bugs: Check for the NULL pointer after calling kmalloc

From: Greg Kroah-Hartman
Date: Mon Jun 13 2022 - 10:12:06 EST

From: Jiasheng Jiang <jiasheng@xxxxxxxxxxx>

[ Upstream commit 4a9800c81d2f34afb66b4b42e0330ae8298019a2 ]

As the possible failure of the kmalloc(), the not_checked and checked
could be NULL pointer.
Therefore, it should be better to check it in order to avoid the
dereference of the NULL pointer.
Also, we need to kfree the 'not_checked' and 'checked' to avoid
the memory leak if fails.
And since it is just a test, it may directly return without error

Fixes: ae2e1aad3e48 ("drivers/misc/lkdtm/bugs.c: add arithmetic overflow and array bounds checks")
Signed-off-by: Jiasheng Jiang <jiasheng@xxxxxxxxxxx>
Acked-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220120092936.1874264-1-jiasheng@xxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/misc/lkdtm/bugs.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index f21854ac5cc2..4f2808b2ca3c 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -327,6 +327,11 @@ void lkdtm_ARRAY_BOUNDS(void)

not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
+ if (!not_checked || !checked) {
+ kfree(not_checked);
+ kfree(checked);
+ return;
+ }

pr_info("Array access within bounds ...\n");
/* For both, touch all bytes in the actual member size. */