[PATCH AUTOSEL 5.15 37/50] lib/test_lockup: fix kernel pointer check for separate address spaces

Sasha Levin
2022-03-30T12:10:44Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 5a06fcb15b43d1f7bf740c672950122331cb5655 ]

test_kernel_ptr() uses access_ok() to figure out if a given address
points to user space instead of kernel space. However on architectures
that set CONFIG_ALTERNATE_USER_ADDRESS_SPACE, a pointer can be valid
for both, and the check always fails because access_ok() returns true.

Make the check for user space pointers conditional on the type of
address space layout.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/test_lockup.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/lib/test_lockup.c b/lib/test_lockup.c
index 6a0f329a794a..c3fd87d6c2dd 100644
--- a/lib/test_lockup.c
+++ b/lib/test_lockup.c
@@ -417,9 +417,14 @@ static bool test_kernel_ptr(unsigned long addr, int size)
return false;

/* should be at least readable kernel address */
- if (access_ok((void __user *)ptr, 1) ||
- access_ok((void __user *)ptr + size - 1, 1) ||
- get_kernel_nofault(buf, ptr) ||
+ if (!IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) &&
+ (access_ok((void __user *)ptr, 1) ||
+ access_ok((void __user *)ptr + size - 1, 1))) {
+ pr_err("user space ptr invalid in kernel: %#lx\n", addr);
+ return true;
+ }
+
+ if (get_kernel_nofault(buf, ptr) ||
get_kernel_nofault(buf, ptr + size - 1)) {
pr_err("invalid kernel ptr: %#lx\n", addr);
return true;
--
2.34.1