linux-kernel - [PATCH 3.2 046/153] signal/openrisc: Fix do_unaligned

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Date:   Wed, 30 May 2018 11:52:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Stefan Kristiansson" <stefan.kristiansson@...nalahti.fi>,
        "Jonas Bonn" <jonas@...thpole.se>, "Arnd Bergmann" <arnd@...db.de>,
        "Stafford Horne" <shorne@...il.com>, openrisc@...ts.librecores.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 3.2 046/153] signal/openrisc: Fix do_unaligned_access to
 send the proper signal

3.2.102-rc1 review patch.  If anyone has any objections, please let me know.

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

From: "Eric W. Biederman" <ebiederm@...ssion.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@...thpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
Cc: Stafford Horne <shorne@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: openrisc@...ts.librecores.org
Acked-by: Stafford Horne <shorne@...il.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -313,12 +313,12 @@ 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);