Calling dump_backtrace() with a pt_regs argument corresponding to userspace doesn't make any sense and our unwinder will simply print "Call trace:" before unwinding the stack looking for user frames.

Rather than go through this song and dance, just return early if we're passed a user register state.

Cc: stable@vger.kernel.org Fixes: 1149aad10b1e ("arm64: Add dump_backtrace() in show_regs") Reported-by: Kefeng Wang wangkefeng.wang@huawei.com Signed-off-by: Will Deacon will.deacon@arm.com --- arch/arm64/kernel/traps.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 8ad119c3f665..29755989f616 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -102,10 +102,16 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame; - int skip; + int skip = 0;

pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);

+ if (regs) { + if (user_mode(regs)) + return; + skip = 1; + } + if (!tsk) tsk = current;

@@ -126,7 +132,6 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) frame.graph = 0; #endif

- skip = !!regs; printk("Call trace:\n"); do { /* skip until specified stack frame */ @@ -176,15 +181,13 @@ static int __die(const char *str, int err, struct pt_regs *regs) return ret;

print_modules(); - __show_regs(regs); pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n", TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), end_of_stack(tsk)); + show_regs(regs);

- if (!user_mode(regs)) { - dump_backtrace(regs, tsk); + if (!user_mode(regs)) dump_instr(KERN_EMERG, regs); - }

return ret; }