From 20955746320e252b41c6b3505587766012e3e06d Mon Sep 17 00:00:00 2001 From: Vasily Gorbik Date: Thu, 20 Jun 2019 10:18:31 +0200 Subject: [PATCH] s390/kasan: avoid false positives during stack unwind Avoid kasan false positive when current task is interrupted in-between stack frame allocation and backchain write instructions leaving new stack frame backchain invalid. In particular if backchain is 0 the unwinder tries to read pt_regs from the stack and might hit kasan poisoned bytes, leading to kasan "stack-out-of-bounds" report. Disable kasan instrumentation of unwinder stack reads, since this limitation couldn't be handled otherwise with current backchain unwinder implementation. Fixes: 78c98f907413 ("s390/unwind: introduce stack unwind API") Reported-by: Julian Wiedmann Tested-by: Benjamin Block Signed-off-by: Vasily Gorbik --- arch/s390/kernel/unwind_bc.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/s390/kernel/unwind_bc.c b/arch/s390/kernel/unwind_bc.c index 57fd4e902f1f..3ce8a0808059 100644 --- a/arch/s390/kernel/unwind_bc.c +++ b/arch/s390/kernel/unwind_bc.c @@ -46,18 +46,18 @@ bool unwind_next_frame(struct unwind_state *state) regs = state->regs; if (unlikely(regs)) { - sp = READ_ONCE_TASK_STACK(state->task, regs->gprs[15]); + sp = READ_ONCE_NOCHECK(regs->gprs[15]); if (unlikely(outside_of_stack(state, sp))) { if (!update_stack_info(state, sp)) goto out_err; } sf = (struct stack_frame *) sp; - ip = READ_ONCE_TASK_STACK(state->task, sf->gprs[8]); + ip = READ_ONCE_NOCHECK(sf->gprs[8]); reliable = false; regs = NULL; } else { sf = (struct stack_frame *) state->sp; - sp = READ_ONCE_TASK_STACK(state->task, sf->back_chain); + sp = READ_ONCE_NOCHECK(sf->back_chain); if (likely(sp)) { /* Non-zero back-chain points to the previous frame */ if (unlikely(outside_of_stack(state, sp))) { @@ -65,7 +65,7 @@ bool unwind_next_frame(struct unwind_state *state) goto out_err; } sf = (struct stack_frame *) sp; - ip = READ_ONCE_TASK_STACK(state->task, sf->gprs[8]); + ip = READ_ONCE_NOCHECK(sf->gprs[8]); reliable = true; } else { /* No back-chain, look for a pt_regs structure */ @@ -73,9 +73,9 @@ bool unwind_next_frame(struct unwind_state *state) if (!on_stack(info, sp, sizeof(struct pt_regs))) goto out_stop; regs = (struct pt_regs *) sp; - if (user_mode(regs)) + if (READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE) goto out_stop; - ip = READ_ONCE_TASK_STACK(state->task, regs->psw.addr); + ip = READ_ONCE_NOCHECK(regs->psw.addr); reliable = true; } } @@ -132,11 +132,11 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, /* Get the instruction pointer from pt_regs or the stack frame */ if (regs) { - ip = READ_ONCE_TASK_STACK(state->task, regs->psw.addr); + ip = READ_ONCE_NOCHECK(regs->psw.addr); reliable = true; } else { sf = (struct stack_frame *) sp; - ip = READ_ONCE_TASK_STACK(state->task, sf->gprs[8]); + ip = READ_ONCE_NOCHECK(sf->gprs[8]); reliable = false; }