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    Subject[PATCH 4.9 080/101] nios2: traced syscall does need to check the syscall number
    Date
    From: Al Viro <viro@zeniv.linux.org.uk>

    commit 25ba820ef36bdbaf9884adeac69b6e1821a7df76 upstream.

    all checks done before letting the tracer modify the register
    state are worthless...

    Fixes: 82ed08dd1b0e ("nios2: Exception handling")
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/nios2/kernel/entry.S | 11 ++++++++---
    1 file changed, 8 insertions(+), 3 deletions(-)

    --- a/arch/nios2/kernel/entry.S
    +++ b/arch/nios2/kernel/entry.S
    @@ -255,9 +255,9 @@ traced_system_call:
    ldw r6, PT_R6(sp)
    ldw r7, PT_R7(sp)

    - /* Fetch the syscall function, we don't need to check the boundaries
    - * since this is already done.
    - */
    + /* Fetch the syscall function. */
    + movui r1, __NR_syscalls
    + bgeu r2, r1, traced_invsyscall
    slli r1, r2, 2
    movhi r11,%hiadj(sys_call_table)
    add r1, r1, r11
    @@ -287,6 +287,11 @@ end_translate_rc_and_ret2:
    RESTORE_SWITCH_STACK
    br ret_from_exception

    + /* If the syscall number was invalid return ENOSYS */
    +traced_invsyscall:
    + movi r2, -ENOSYS
    + br translate_rc_and_ret2
    +
    Luser_return:
    GET_THREAD_INFO r11 /* get thread_info pointer */
    ldw r10, TI_FLAGS(r11) /* get thread_info->flags */

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