On 12/18/2017 07:36 PM, Alexei Starovoitov wrote:
> On 12/18/17 10:19 AM, Daniel Borkmann wrote:
>> On 12/18/2017 07:09 PM, Alexei Starovoitov wrote:
>>> From: Alexei Starovoitov <a...@fb.com>
>>>
>>> fix the following issue:
>>> arch/arm64/net/bpf_jit_comp.c: In function 'bpf_int_jit_compile':
>>> arch/arm64/net/bpf_jit_comp.c:982:18: error: 'image_size' may be used
>>> uninitialized in this function [-Werror=maybe-uninitialized]
>>>
>>> Fixes: db496944fdaa ("bpf: arm64: add JIT support for multi-function
>>> programs")
>>> Reported-by: Arnd Bergmann <a...@arndb.de>
>>> Signed-off-by: Alexei Starovoitov <a...@kernel.org>
>>> ---
>>> arch/arm64/net/bpf_jit_comp.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
>>> index 396490cf7316..acaa935ed977 100644
>>> --- a/arch/arm64/net/bpf_jit_comp.c
>>> +++ b/arch/arm64/net/bpf_jit_comp.c
>>> @@ -897,6 +897,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog
>>> *prog)
>>> image_ptr = jit_data->image;
>>> header = jit_data->header;
>>> extra_pass = true;
>>> + image_size = sizeof(u32) * ctx.idx;
>>> goto skip_init_ctx;
>>> }
>>> memset(&ctx, 0, sizeof(ctx));
>>
>> I don't really mind, but it feels more complex than it needs to be
>> imho, since in the initial pass you fetch 'image_size' in fake pass
>> from ctx.idx, then we set ctx.idx to 0 again, do another pass and
>> use the cached ctx.idx from that second pass instead of the first
>> one where we set 'image_size' originally, so we definitely need to
>> take that into consideration in future reviews at least.
>
> not sure what you mean.
> This check: ctx.idx != jit_data->ctx.idx matters the most.
> After first alloc the 'image_size' variable used for dumping only.
> That's why the JITing itself worked fine. We could have removed it
> since it's computable from idx, but imo it's fine this way.
Fair enough, given final ctx.idx value must be guaranteed to never change
in future between pass#1 and pass#2 from the first bpf_int_jit_compile()
run, then lets go with this smaller version; applied to bpf-next, thanks
Alexei!
