[PATCH 2/4] score: signal: fix sigaltstack check

[Stas Sergeev]

Currently get_sigframe() checks only
(ka->sa.sa_flags & SA_ONSTACK) && (!on_sig_stack(sp))
to determine whether the switch to sigaltstack is needed.
It forgets to checks whether the sigaltstack was previously set.

This patch replaces the !on_sig_stack(sp) with the standard check
sas_ss_flags(sp) == 0
that takes into account both conditions: it succeeds only if the
sigaltstack is enabled but currently not active.

CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: linux-kernel@xxxxxxxxxxxxxxx
CC: Chen Liqin <liqin.linux@xxxxxxxxx>
CC: Lennox Wu <lennox.wu@xxxxxxxxx>
CC: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: James Hogan <james.hogan@xxxxxxxxxx>

Signed-off-by: Stas Sergeev <stsp@xxxxxxxxxxxxxxxxxxxxx>
---
 arch/score/kernel/signal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/score/kernel/signal.c b/arch/score/kernel/signal.c
index e381c8c..bd1c7c8 100644
--- a/arch/score/kernel/signal.c
+++ b/arch/score/kernel/signal.c
@@ -127,7 +127,7 @@ static void __user *get_sigframe(struct k_sigaction *ka,
     sp -= 32;

     /* This is the X/Open sanctioned signal stack switching.  */
-    if ((ka->sa.sa_flags & SA_ONSTACK) && (!on_sig_stack(sp)))
+    if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
         sp = current->sas_ss_sp + current->sas_ss_size;

     return (void __user*)((sp - frame_size) & ~7);
--
2.5.0