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    Subject[PATCH AUTOSEL 5.16 41/59] lib/test_lockup: fix kernel pointer check for separate address spaces
    Date
    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
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