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s390/kasan: avoid false positives during stack unwind

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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: 78c98f9074 ("s390/unwind: introduce stack unwind API")
Reported-by: Julian Wiedmann <jwi@linux.ibm.com>
Tested-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2019-06-20 10:18:31 +02:00
parent ac6639cd3d
commit 2095574632
1 changed files with 8 additions and 8 deletions
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16
arch/s390/kernel/unwind_bc.c
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@ -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;
}