| Message ID | 03f4e86a029058d0f674fd9bf288e55a5ec07df3.1503104831.git.daniel@iogearbox.net |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On 8/18/17 6:12 PM, Daniel Borkmann wrote: > Commit 9015d2f59535 ("bpf: inline htab_map_lookup_elem()") was > making the assumption that a direct call emission to the function > __htab_map_lookup_elem() will always work out for JITs. > > This is currently true since all JITs we have are for 64 bit archs, > but in case of 32 bit JITs like upcoming arm32, we get a NULL pointer > dereference when executing the call to __htab_map_lookup_elem() > since passed arguments are of a different size (due to pointer args) > than what we do out of BPF. Guard and thus limit this for now for > the current 64 bit JITs only. > > Reported-by: Shubham Bansal <illusionist.neo@gmail.com> > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Thanks. That's good robustness fix.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4f6e7eb..e42c096 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4160,7 +4160,11 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) continue; } - if (ebpf_jit_enabled() && insn->imm == BPF_FUNC_map_lookup_elem) { + /* BPF_EMIT_CALL() assumptions in some of the map_gen_lookup + * handlers are currently limited to 64 bit only. + */ + if (ebpf_jit_enabled() && BITS_PER_LONG == 64 && + insn->imm == BPF_FUNC_map_lookup_elem) { map_ptr = env->insn_aux_data[i + delta].map_ptr; if (map_ptr == BPF_MAP_PTR_POISON || !map_ptr->ops->map_gen_lookup)
Commit 9015d2f59535 ("bpf: inline htab_map_lookup_elem()") was making the assumption that a direct call emission to the function __htab_map_lookup_elem() will always work out for JITs. This is currently true since all JITs we have are for 64 bit archs, but in case of 32 bit JITs like upcoming arm32, we get a NULL pointer dereference when executing the call to __htab_map_lookup_elem() since passed arguments are of a different size (due to pointer args) than what we do out of BPF. Guard and thus limit this for now for the current 64 bit JITs only. Reported-by: Shubham Bansal <illusionist.neo@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> --- kernel/bpf/verifier.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)