Re: [PATCH v5 06/11] perf symbol: Get rid of machine_or_dso_e_machine()

[Namhyung Kim <namhyung@kernel.org>]

On Tue, Oct 13, 2026 at 05:37:49PM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] perf symbol: NULL pointer dereference in dso__load() on error path
> --
> 
> commit a7899d8622f5885c1647a9ddbd7a9ae67999aeeb
> Author: Namhyung Kim <namhyung@kernel.org>
> 
> perf symbol: Get rid of machine_or_dso_e_machine()
> 
> This commit removes the machine_or_dso_e_machine() fallback logic and relies
> directly on perf_env__e_machine() for kernel maps. It aims to prevent
> recursive locking issues and assumes kernel DSO architectures are correctly
> described by the machine environment.
> 
> > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> > index 56b8d75966133..a7afecb5816c2 100644
> > --- a/tools/perf/util/symbol.c
> > +++ b/tools/perf/util/symbol.c
> [ ... ]
> > @@ -1855,7 +1838,7 @@ int dso__load(struct dso *dso, struct map *map)
> >  			ret = dso__load_guest_kernel_sym(dso, map);
> >  
> >  		machine = maps__machine(map__kmaps(map));
> > -		if (machine && machine_or_dso_e_machine(machine, dso) == EM_X86_64)
> > +		if (perf_env__e_machine(machine->env, /*e_flags=*/NULL) == EM_X86_64)
> 
> [Severity: Medium]
> Does this code cause a NULL pointer dereference if machine is NULL?
> 
> By removing the machine pointer guard, if map__kmaps() returns NULL (for
> example, if a kernel DSO is incorrectly associated with a non-kernel map from a
> malformed perf.data file), maps__machine() will also return NULL. Passing
> machine->env directly to perf_env__e_machine() in this state will then trigger
> a segfault.
> 
> Could the machine check be restored before attempting to read its environment?

I believe machine cannot be NULL when it's from a kmap.  In fact, I
think we'd better guarantee it's non-NULL for all cases.  IIUC only case
it can be NULL is a test case (and it's not a kmap).  I think it's better
to update the test not to pass NULL instead.

Thanks,
Namhyung

> 
> >  			machine__map_x86_64_entry_trampolines(machine, dso);
> >  		goto out;
> >  	}
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20261013172155.160869-1-namhyung@kernel.org?part=6