[Devel] [PATCH RHEL7 COMMIT] ms/x86/signal: Remove bogus user_64bit_mode() check from sigaction_compat_abi()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.36.1.vz7.20.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.36.1.vz7.20.3
------>
commit b35cf83c488e6885f44a95c4aecbf11033bdf117
Author: Dmitry Safonov <dsafonov at virtuozzo.com>
Date:   Fri Nov 25 18:28:39 2016 +0400

    ms/x86/signal: Remove bogus user_64bit_mode() check from sigaction_compat_abi()
    
    Fix for 32-bit C/R patches
    
    There is backport of mainstream fix for 32-bit C/R patches.
    Backport it as it fixes x32 support (do not confuse with ia32 support).
    Not sure if anyone uses x32 - it's quite rare thing, but anyway,
    let's have it.
    
    ====================
    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 9c6c4de..cbd5c5a 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())