linux-kernel - [PATCH 4.4 36/93] MIPS: uprobes: fix use of uninitialised variable

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Date:   Thu,  6 Oct 2016 10:29:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Marcin Nowakowski <marcin.nowakowski@...tec.com>,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 4.4 36/93] MIPS: uprobes: fix use of uninitialised variable

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Marcin Nowakowski <marcin.nowakowski@...tec.com>

commit ca86c9ef2b322ebf24772009fdea037688cbdac1 upstream.

arch_uprobe_pre_xol needs to emulate a branch if a branch instruction
has been replaced with a breakpoint, but in fact an uninitialised local
variable was passed to the emulator routine instead of the original
instruction

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@...tec.com>
Fixes: 40e084a506eb ('MIPS: Add uprobes support.')
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14300/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/kernel/uprobes.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/arch/mips/kernel/uprobes.c
+++ b/arch/mips/kernel/uprobes.c
@@ -157,7 +157,6 @@ bool is_trap_insn(uprobe_opcode_t *insn)
 int arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs)
 {
 	struct uprobe_task *utask = current->utask;
-	union mips_instruction insn;
 
 	/*
 	 * Now find the EPC where to resume after the breakpoint has been
@@ -168,10 +167,10 @@ int arch_uprobe_pre_xol(struct arch_upro
 		unsigned long epc;
 
 		epc = regs->cp0_epc;
-		__compute_return_epc_for_insn(regs, insn);
+		__compute_return_epc_for_insn(regs,
+			(union mips_instruction) aup->insn[0]);
 		aup->resume_epc = regs->cp0_epc;
 	}
-
 	utask->autask.saved_trap_nr = current->thread.trap_nr;
 	current->thread.trap_nr = UPROBE_TRAP_NR;
 	regs->cp0_epc = current->utask->xol_vaddr;