[Devel] [PATCH RH7] ms/x86/signal: Remove bogus user_64bit_mode() check from sigaction_compat_abi()

[Dmitry Safonov]

The recent introduction of SA_X32/IA32 sa_flags added a check for
user_64bit_mode() into sigaction_compat_abi(). user_64bit_mode() is true
for native 64-bit processes and x32 processes.

Due to that the function returns w/o setting the SA_X32_ABI flag for X32
processes. In consequence the kernel attempts to deliver the signal to the
X32 process in native 64-bit mode causing the process to segfault.

Remove the check, so the actual check for X32 mode which sets the ABI flag
can be reached. There is no side effect for native 64-bit mode.

[ tglx: Rewrote changelog ]

Fixes: 6846351052e6 ("x86/signal: Add SA_{X32,IA32}_ABI sa_flags")
Reported-by: Mikulas Patocka <mpatocka at redhat.com>
Tested-by: Adam Borowski <kilobyte at angband.pl>
Signed-off-by: Dmitry Safonov <0x7f454c46 at gmail.com>
Cc: Dmitry Safonov <dsafonov at virtuozzo.com>
Cc: Oleg Nesterov <oleg at redhat.com>
Cc: linux-mm at kvack.org
Cc: Cyrill Gorcunov <gorcunov at openvz.org>
Cc: Pavel Emelyanov <xemul at virtuozzo.com>
Link: http://lkml.kernel.org/r/CAJwJo6Z8ZWPqNfT6t-i8GW1MKxQrKDUagQqnZ%2B0%2B697%3DMyVeGg@mail.gmail.com
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Dmitry Safonov <dsafonov at virtuozzo.com>

[backported from ms commit ed1e7db33c33 ("x86/signal: Remove bogus
user_64bit_mode() check from sigaction_compat_abi()")]
Signed-off-by: Dmitry Safonov <dsafonov at virtuozzo.com>
---
 arch/x86/ia32/ia32_signal.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 9c6c4de8da46..cbd5c5ad5edf 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -47,9 +47,6 @@ void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
 	/* Don't let flags to be set from userspace */
 	act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
 
-	if (user_64bit_mode(current_pt_regs()))
-		return;
-
 	if (is_ia32_task())
 		act->sa.sa_flags |= SA_IA32_ABI;
 	if (is_x32_task())
-- 
2.10.1