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authorJames Hogan <james.hogan@imgtec.com>2017-06-29 17:05:04 +0300
committerRalf Baechle <ralf@linux-mips.org>2017-06-30 05:42:15 +0300
commit854236363370995a609a10b03e35fd3dc5e9e4a1 (patch)
tree018ed1df38ce86f1576e664a3104de867ec95028
parentcad482c1b1844136fc6d9e33f10d3386344fb045 (diff)
downloadlinux-854236363370995a609a10b03e35fd3dc5e9e4a1.tar.xz
MIPS: Avoid accidental raw backtrace
Since commit 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode") show_backtrace() invokes the raw backtracer when cp0_status & ST0_KSU indicates user mode to fix issues on EVA kernels where user and kernel address spaces overlap. However this is used by show_stack() which creates its own pt_regs on the stack and leaves cp0_status uninitialised in most of the code paths. This results in the non deterministic use of the raw back tracer depending on the previous stack content. show_stack() deals exclusively with kernel mode stacks anyway, so explicitly initialise regs.cp0_status to KSU_KERNEL (i.e. 0) to ensure we get a useful backtrace. Fixes: 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode") Signed-off-by: James Hogan <james.hogan@imgtec.com> Cc: linux-mips@linux-mips.org Cc: <stable@vger.kernel.org> # 3.15+ Patchwork: https://patchwork.linux-mips.org/patch/16656/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
-rw-r--r--arch/mips/kernel/traps.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 9681b5877140..38dfa27730ff 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -201,6 +201,8 @@ void show_stack(struct task_struct *task, unsigned long *sp)
{
struct pt_regs regs;
mm_segment_t old_fs = get_fs();
+
+ regs.cp0_status = KSU_KERNEL;
if (sp) {
regs.regs[29] = (unsigned long)sp;
regs.regs[31] = 0;