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    Subject[PATCH 4.9 153/172] x86/mpx: Correctly report do_mpx_bt_fault() failures to user-space
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Joerg Roedel <jroedel@suse.de>

    commit 5ed386ec09a5d75bcf073967e55e895c2607a5c3 upstream.

    When this function fails it just sends a SIGSEGV signal to
    user-space using force_sig(). This signal is missing
    essential information about the cause, e.g. the trap_nr or
    an error code.

    Fix this by propagating the error to the only caller of
    mpx_handle_bd_fault(), do_bounds(), which sends the correct
    SIGSEGV signal to the process.

    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Fixes: fe3d197f84319 ('x86, mpx: On-demand kernel allocation of bounds tables')
    Link: http://lkml.kernel.org/r/1491488362-27198-1-git-send-email-joro@8bytes.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/mm/mpx.c | 10 +---------
    1 file changed, 1 insertion(+), 9 deletions(-)

    --- a/arch/x86/mm/mpx.c
    +++ b/arch/x86/mm/mpx.c
    @@ -525,15 +525,7 @@ int mpx_handle_bd_fault(void)
    if (!kernel_managing_mpx_tables(current->mm))
    return -EINVAL;

    - if (do_mpx_bt_fault()) {
    - force_sig(SIGSEGV, current);
    - /*
    - * The force_sig() is essentially "handling" this
    - * exception, so we do not pass up the error
    - * from do_mpx_bt_fault().
    - */
    - }
    - return 0;
    + return do_mpx_bt_fault();
    }

    /*

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