Messages in this thread | | | Subject | Re: linux-next: manual merge of the net-next tree with the net tree | From | Yonghong Song <> | Date | Fri, 19 Mar 2021 08:17:17 -0700 |
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On 3/19/21 12:21 AM, Daniel Borkmann wrote: > On 3/19/21 3:11 AM, Piotr Krysiuk wrote: >> Hi Daniel, >> >> On Fri, Mar 19, 2021 at 12:16 AM Stephen Rothwell <sfr@canb.auug.org.au> >> wrote: >> >>> diff --cc kernel/bpf/verifier.c >>> index 44e4ec1640f1,f9096b049cd6..000000000000 >>> --- a/kernel/bpf/verifier.c >>> +++ b/kernel/bpf/verifier.c >>> @@@ -5876,10 -6056,22 +6060,23 @@@ static int >>> retrieve_ptr_limit(const str >>> if (mask_to_left) >>> *ptr_limit = MAX_BPF_STACK + off; >>> else >>> - *ptr_limit = -off; >>> - return 0; >>> + *ptr_limit = -off - 1; >>> + return *ptr_limit >= max ? -ERANGE : 0; >>> + case PTR_TO_MAP_KEY: >>> + /* Currently, this code is not exercised as the only use >>> + * is bpf_for_each_map_elem() helper which requires >>> + * bpf_capble. The code has been tested manually for >>> + * future use. >>> + */ >>> + if (mask_to_left) { >>> + *ptr_limit = ptr_reg->umax_value + ptr_reg->off; >>> + } else { >>> + off = ptr_reg->smin_value + ptr_reg->off; >>> + *ptr_limit = ptr_reg->map_ptr->key_size - off; >>> + } >>> + return 0; >>> >> >> PTR_TO_MAP_VALUE logic above looks like copy-paste of old >> PTR_TO_MAP_VALUE >> code from before "bpf: Fix off-by-one for area size in creating mask to >> left" and is apparently affected by the same off-by-one, except this time >> on "key_size" area and not "value_size". >> >> This needs to be fixed in the same way as we did with PTR_TO_MAP_VALUE. >> What is the best way to proceed? > > Hm, not sure why PTR_TO_MAP_KEY was added by 69c087ba6225 in the first > place, I > presume noone expects this to be used from unprivileged as the comment > says. > Resolution should be to remove the PTR_TO_MAP_KEY case entirely from > that switch > until we have an actual user.
Alexei suggested so that we don't forget it in the future if bpf_capable() requirement is removed. https://lore.kernel.org/bpf/c837ae55-2487-2f39-47f6-a18781dc6fcc@fb.com/
I am okay with either way, fix it or remove it.
> > Thanks, > Daniel
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