Messages in this thread | | | Date | Wed, 23 Feb 2022 09:16:32 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 04/29] x86/livepatch: Validate __fentry__ location |
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On Wed, 23 Feb 2022 15:05:42 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Feb 23, 2022 at 07:41:39AM -0500, Steven Rostedt wrote: > > On Wed, 23 Feb 2022 11:57:26 +0100 > > Peter Zijlstra <peterz@infradead.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. > > > > # git grep ftrace_location > arch/powerpc/include/asm/livepatch.h:#define klp_get_ftrace_location klp_get_ftrace_location > arch/powerpc/include/asm/livepatch.h:static inline unsigned long klp_get_ftrace_location(unsigned long faddr) > arch/powerpc/include/asm/livepatch.h: return ftrace_location_range(faddr, faddr + 16); > arch/powerpc/kernel/kprobes.c: faddr = ftrace_location_range((unsigned long)addr, > arch/x86/kernel/kprobes/core.c: faddr = ftrace_location(addr); > arch/x86/kernel/kprobes/core.c: * arch_check_ftrace_location(). Something went terribly wrong > include/linux/ftrace.h:unsigned long ftrace_location(unsigned long ip); > include/linux/ftrace.h:unsigned long ftrace_location_range(unsigned long start, unsigned long end); > include/linux/ftrace.h:static inline unsigned long ftrace_location(unsigned long ip) > kernel/bpf/trampoline.c:static int is_ftrace_location(void *ip) > kernel/bpf/trampoline.c: addr = ftrace_location((long)ip); > kernel/bpf/trampoline.c: ret = is_ftrace_location(ip); > kernel/kprobes.c: unsigned long faddr = ftrace_location((unsigned long)addr); > kernel/kprobes.c:static int check_ftrace_location(struct kprobe *p) > kernel/kprobes.c: ftrace_addr = ftrace_location((unsigned long)p->addr); > kernel/kprobes.c: ret = check_ftrace_location(p); > kernel/livepatch/patch.c:#ifndef klp_get_ftrace_location > kernel/livepatch/patch.c:static unsigned long klp_get_ftrace_location(unsigned long faddr) > kernel/livepatch/patch.c: return ftrace_location(faddr); > kernel/livepatch/patch.c: klp_get_ftrace_location((unsigned long)func->old_func); > kernel/livepatch/patch.c: klp_get_ftrace_location((unsigned long)func->old_func); > kernel/trace/ftrace.c: * ftrace_location_range - return the first address of a traced location > kernel/trace/ftrace.c:unsigned long ftrace_location_range(unsigned long start, unsigned long end) > kernel/trace/ftrace.c: * ftrace_location - return true if the ip giving is a traced location > kernel/trace/ftrace.c:unsigned long ftrace_location(unsigned long ip) > kernel/trace/ftrace.c: ret = ftrace_location_range((unsigned long)start, > kernel/trace/ftrace.c: if (!ftrace_location(ip)) > kernel/trace/ftrace.c: ip = ftrace_location(ip); > kernel/trace/ftrace.c: ip = ftrace_location(ip); > kernel/trace/trace_kprobe.c: * Since ftrace_location_range() does inclusive range check, we need > kernel/trace/trace_kprobe.c: return !ftrace_location_range(addr, addr + size - 1); > > and yet almost every caller takes the address it returns...
And they check if the returned value is 0 or not. If it is zero, it lets them know it isn't an ftrace location.
-- Steve
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