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| author | James Hogan <james.hogan@imgtec.com> | 2017-06-29 17:05:04 +0300 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2017-06-30 05:42:15 +0300 |
| commit | 854236363370995a609a10b03e35fd3dc5e9e4a1 (patch) | |
| tree | 018ed1df38ce86f1576e664a3104de867ec95028 | |
| parent | cad482c1b1844136fc6d9e33f10d3386344fb045 (diff) | |
| download | linux-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.c | 2 |
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; |