linux-kernel - [PATCH 3.2 56/62] MIPS: traps: Fix SIGFPE information leak from `do_ov' and `do_trap_or

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Date:	Tue, 29 Mar 2016 20:18:22 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Maciej W. Rozycki" <macro@...tec.com>,
	"Ralf Baechle" <ralf@...ux-mips.org>
Subject: [PATCH 3.2 56/62] MIPS: traps: Fix SIGFPE information leak from
 `do_ov' and `do_trap_or_bp'

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

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

From: "Maciej W. Rozycki" <macro@...tec.com>

commit e723e3f7f9591b79e8c56b3d7c5a204a9c571b55 upstream.

Avoid sending a partially initialised `siginfo_t' structure along SIGFPE
signals issued from `do_ov' and `do_trap_or_bp', leading to information
leaking from the kernel stack.

Signed-off-by: Maciej W. Rozycki <macro@...tec.com>
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/mips/kernel/traps.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -656,14 +656,14 @@ static int simulate_sync(struct pt_regs
 
 asmlinkage void do_ov(struct pt_regs *regs)
 {
-	siginfo_t info;
+	siginfo_t info = {
+		.si_signo = SIGFPE,
+		.si_code = FPE_INTOVF,
+		.si_addr = (void __user *)regs->cp0_epc,
+	};
 
 	die_if_kernel("Integer overflow", regs);
 
-	info.si_code = FPE_INTOVF;
-	info.si_signo = SIGFPE;
-	info.si_errno = 0;
-	info.si_addr = (void __user *) regs->cp0_epc;
 	force_sig_info(SIGFPE, &info, current);
 }
 
@@ -758,7 +758,7 @@ asmlinkage void do_fpe(struct pt_regs *r
 static void do_trap_or_bp(struct pt_regs *regs, unsigned int code,
 	const char *str)
 {
-	siginfo_t info;
+	siginfo_t info = { 0 };
 	char b[40];
 
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
@@ -785,7 +785,6 @@ static void do_trap_or_bp(struct pt_regs
 		else
 			info.si_code = FPE_INTOVF;
 		info.si_signo = SIGFPE;
-		info.si_errno = 0;
 		info.si_addr = (void __user *) regs->cp0_epc;
 		force_sig_info(SIGFPE, &info, current);
 		break;