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| author | James Hogan <james.hogan@imgtec.com> | 2017-06-29 14:05:04 (GMT) |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-07-05 12:40:17 (GMT) |
| commit | f7d3d40ea1242f633bbf093b63181acff2da319e (patch) | |
| tree | 5d737d29230cbd4e4a151bde687dec4a4520f272 /arch/mips | |
| parent | 3d4ac49a9538c36d9c3c121ddbcb4c3958dee5e9 (diff) | |
| download | linux-f7d3d40ea1242f633bbf093b63181acff2da319e.tar.xz | |
MIPS: Avoid accidental raw backtrace
commit 854236363370995a609a10b03e35fd3dc5e9e4a1 upstream.
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
Patchwork: https://patchwork.linux-mips.org/patch/16656/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/mips')
| -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 ec87ef9..b0b29cb 100644 --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -199,6 +199,8 @@ 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; |