[PATCH 4.4 091/101] x86/mpx: Correctly report do_mpx_bt_fault() failures to user-space

From: Greg Kroah-Hartman
Date: Mon Jul 03 2017 - 10:49:57 EST

4.4-stable review patch. If anyone has any objections, please let me know.


From: Joerg Roedel <jroedel@xxxxxxx>

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@xxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fixes: fe3d197f84319 ('x86, mpx: On-demand kernel allocation of bounds tables')
Link: http://lkml.kernel.org/r/1491488362-27198-1-git-send-email-joro@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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();