Messages in this thread | | | Date | Wed, 23 Feb 2022 09:23:27 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 04/29] x86/livepatch: Validate __fentry__ location |
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On Wed, 23 Feb 2022 07:41:39 -0500 Steven Rostedt <rostedt@goodmis.org> wrote:
> > --- a/kernel/trace/ftrace.c > > +++ b/kernel/trace/ftrace.c > > @@ -1578,7 +1578,23 @@ unsigned long ftrace_location_range(unsi > > */ > > unsigned long ftrace_location(unsigned long ip) > > { > > - return ftrace_location_range(ip, ip); > > + struct dyn_ftrace *rec; > > + unsigned long offset; > > + unsigned long size; > > + > > + rec = lookup_rec(ip, ip); > > + if (!rec) { > > + if (!kallsyms_lookup_size_offset(ip, &size, &offset)) > > + goto out; > > + > > + rec = lookup_rec(ip - offset, (ip - offset) + size); > > + } > > + > > Please create a new function for this. Perhaps find_ftrace_location(). > > ftrace_location() is used to see if the address given is a ftrace > nop or not. This change will make it always return true.
Now we could do:
return ip <= (rec->ip + MCOUNT_INSN_SIZE) ? rec->ip : 0;
Since we would want rec->ip if the pointer is before the ftrace instruction. But we would need to audit all use cases and make sure this is not called from any hot paths (in a callback).
This will affect kprobes and BPF as they both use ftrace_location() as well.
-- Steve
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