Messages in this thread | | | Subject | Re: linux-next: manual merge of the net-next tree with the net tree | From | Daniel Borkmann <> | Date | Fri, 19 Mar 2021 08:21:15 +0100 |
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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.
Thanks, Daniel
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