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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jonas Bonn <jonas@southpole.se>,
        Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
        Stafford Horne <shorne@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>, openrisc@lists.librecores.org,
        "Eric W. Biederman" <ebiederm@xmission.com>
Subject: [PATCH 4.9 70/88] signal/openrisc: Fix do_unaligned_access to send the proper signal
Date:   Thu, 15 Feb 2018 16:17:37 +0100
Message-Id: <20180215151232.219981528@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric W. Biederman <ebiederm@xmission.com>

commit 500d58300571b6602341b041f97c082a461ef994 upstream.

While reviewing the signal sending on openrisc the do_unaligned_access
function stood out because it is obviously wrong.  A comment about an
si_code set above when actually si_code is never set.  Leading to a
random si_code being sent to userspace in the event of an unaligned
access.

Looking further SIGBUS BUS_ADRALN is the proper pair of signal and
si_code to send for an unaligned access. That is what other
architectures do and what is required by posix.

Given that do_unaligned_access is broken in a way that no one can be
relying on it on openrisc fix the code to just do the right thing.

Fixes: 769a8a96229e ("OpenRISC: Traps")
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: openrisc@lists.librecores.org
Acked-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/openrisc/kernel/traps.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/arch/openrisc/kernel/traps.c
+++ b/arch/openrisc/kernel/traps.c
@@ -302,12 +302,12 @@ asmlinkage void do_unaligned_access(stru
 	siginfo_t info;
 
 	if (user_mode(regs)) {
-		/* Send a SIGSEGV */
-		info.si_signo = SIGSEGV;
+		/* Send a SIGBUS */
+		info.si_signo = SIGBUS;
 		info.si_errno = 0;
-		/* info.si_code has been set above */
-		info.si_addr = (void *)address;
-		force_sig_info(SIGSEGV, &info, current);
+		info.si_code = BUS_ADRALN;
+		info.si_addr = (void __user *)address;
+		force_sig_info(SIGBUS, &info, current);
 	} else {
 		printk("KERNEL: Unaligned Access 0x%.8lx\n", address);
 		show_registers(regs);