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    Subject[PATCH AUTOSEL 5.5 483/542] powerpc/mm: Don't log user reads to 0xffffffff
    Date
    From: Christophe Leroy <christophe.leroy@c-s.fr>

    [ Upstream commit 0f9aee0cb9da7db7d96f63cfa2dc5e4f1bffeb87 ]

    Running vdsotest leaves many times the following log:

    [ 79.629901] vdsotest[396]: User access of kernel address (ffffffff) - exploit attempt? (uid: 0)

    A pointer set to (-1) is likely a programming error similar to
    a NULL pointer and is not worth logging as an exploit attempt.

    Don't log user accesses to 0xffffffff.

    Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/0728849e826ba16f1fbd6fa7f5c6cc87bd64e097.1577087627.git.christophe.leroy@c-s.fr
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/mm/fault.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
    index 1baeb045f7f4b..e083a9f67f701 100644
    --- a/arch/powerpc/mm/fault.c
    +++ b/arch/powerpc/mm/fault.c
    @@ -354,6 +354,9 @@ static void sanity_check_fault(bool is_write, bool is_user,
    * Userspace trying to access kernel address, we get PROTFAULT for that.
    */
    if (is_user && address >= TASK_SIZE) {
    + if ((long)address == -1)
    + return;
    +
    pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n",
    current->comm, current->pid, address,
    from_kuid(&init_user_ns, current_uid()));
    --
    2.20.1
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