On Thu, 2012-09-06 at 17:02 +0200, Robert Richter wrote: > > > --- a/arch/x86/oprofile/backtrace.c > > > +++ b/arch/x86/oprofile/backtrace.c > > > @@ -113,7 +113,7 @@ x86_backtrace(struct pt_regs * const regs, unsigned > > > int depth) > > > > > > if (!user_mode_vm(regs)) { > > > unsigned long stack = kernel_stack_pointer(regs); > > > - if (depth) > > > + if (depth & stack) > > > > Can other users of kernel_stack_pointer() be nailed by a return of NULL? > > It would be save here too, but dump_trace() falls back to the current > stack in case there is no stack address given which we don't want with > oprofile. > > I was looking at all users of kernel_stack_pointer() and could not > find any direct pointer dereference of the sp. The only potential > problems I found could arise here: > > arch/x86/kernel/kprobes.c:resume_execution() > arch/x86/kernel/time.c:profile_pc() > > It is not quite clear if we really need code here that checks the > pointer. Since a NULL pointer access has the same effect as if the > stack address would be wrong which would be the case without the > patch, I rather tend not to change the code here.
Then a comment should be in the oprofile code too. Something to the effect that oprofile is special and can cause kernel_stack_pointer() to return NULL in some cases, thus we need to check for it. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/