x86/mpx: Correctly report do_mpx_bt_fault() failures to user-space

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>

diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index cd44ae727df7f48ceba7fad00591c48cec151896..1c34b767c84ca650386f1b550aa5e3f13d24d5ce 100644 (file)
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -526,15 +526,7 @@ 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();
 }
 
 /*