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bpf: Test DEBUG configurations, fix a newly exposed verifier error #32170

Merged
merged 2 commits into from
May 7, 2024
Merged

bpf: Test DEBUG configurations, fix a newly exposed verifier error #32170

merged 2 commits into from
May 7, 2024

Commits on May 3, 2024

  1. bpf: Fix "same insn cannot be used with different pointers" in proxy.h 

    When DEBUG is enabled, Clang 17 optimizes the final part of
assign_socket_tcp and assign_socket_udp by keeping only one instance of
the code and jumping to it from two places. It means that the same
struct bpf_sock *sk pointer can point to the return value of either
skc_lookup_tcp or sk_lookup_udp. Unfortunately, for the verifier these
pointer types are different (PTR_TO_SOCK_COMMON and PTR_TO_SOCKET), and
it doesn't allow such pattern with the following error:

; sk = sk_lookup_udp(ctx, tuple, len, BPF_F_CURRENT_NETNS, 0);
829: (bf) r1 = r6
830: (b4) w3 = 36
831: (b7) r4 = -1
832: (b7) r5 = 0
833: (85) call bpf_sk_lookup_udp#85
last_idx 833 first_idx 827
regs=8 stack=0 before 832: (b7) r5 = 0
regs=8 stack=0 before 831: (b7) r4 = -1
regs=8 stack=0 before 830: (b4) w3 = 36
834: (b4) w7 = -178
; if (!sk)
835: (15) if r0 == 0x0 goto pc+38
 R0_w=sock(id=0,ref_obj_id=29,off=0,imm=0) R6=ctx(id=0,off=0,imm=0) R7_w=inv4294967118 R8=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R9=inv(id=22,umax_value=65535,var_off=(0x0; 0xffff)) R10=fp0 fp-16=???mmmmm fp-24=mmmmmmmm fp-32=mmmmmmmm fp-40=mmmmmmmm fp-48=mmmmmmmm fp-72=????mmmm fp-80=mmmmmmmm fp-88=mmmmmmmm refs=29
;
836: (61) r1 = *(u32 *)(r6 +16)
837: (63) *(u32 *)(r10 -104) = r1
838: (61) r7 = *(u32 *)(r0 +4)
same insn cannot be used with different pointers
processed 1261 insns (limit 1000000) max_states_per_insn 4 total_states 68 peak_states 67 mark_read 19

Work around it by adding READ_ONCE to the problematic dereference.
Although it doesn't guarantee that the same problem won't happen, it
helps in this case.

Ref: #32169
Fixes: 673d481 ("images: Update LLVM to 17.0.6")
Reported-by: Marco Hofstetter <marco.hofstetter@isovalent.com>
Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>
Co-developed-by: Marco Hofstetter <marco.hofstetter@isovalent.com>
Signed-off-by: Marco Hofstetter <marco.hofstetter@isovalent.com>
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    gentoo-root committed May 3, 2024
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  2. bpf: complexity-tests: Test DEBUG and LB_DEBUG configurations 

    Run the verifier tests on the debug configurations, because it may
expose verifier errors.

Ref: #32169
Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>
    @gentoo-root
    gentoo-root committed May 3, 2024
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