Andrii Nakryiko 10e14e9652 bpf: fix control-flow graph checking in privileged mode ... When BPF program is verified in privileged mode, BPF verifier allows bounded loops. This means that from CFG point of view there are definitely some back-edges. Original commit adjusted check_cfg() logic to not detect back-edges in control flow graph if they are resulting from conditional jumps, which the idea that subsequent full BPF verification process will determine whether such loops are bounded or not, and either accept or reject the BPF program. At least that's my reading of the intent. Unfortunately, the implementation of this idea doesn't work correctly in all possible situations. Conditional jump might not result in immediate back-edge, but just a few unconditional instructions later we can arrive at back-edge. In such situations check_cfg() would reject BPF program even in privileged mode, despite it might be bounded loop. Next patch adds one simple program demonstrating such scenario. To keep things simple, instead of trying to detect back edges in privileged mode, just assume every back edge is valid and let subsequent BPF verification prove or reject bounded loops. Note a few test changes. For unknown reason, we have a few tests that are specified to detect a back-edge in a privileged mode, but looking at their code it seems like the right outcome is passing check_cfg() and letting subsequent verification to make a decision about bounded or not bounded looping. Bounded recursion case is also interesting. The example should pass, as recursion is limited to just a few levels and so we never reach maximum number of nested frames and never exhaust maximum stack depth. But the way that max stack depth logic works today it falsely detects this as exceeding max nested frame count. This patch series doesn't attempt to fix this orthogonal problem, so we just adjust expected verifier failure. Suggested-by: Alexei Starovoitov <ast@kernel.org> Fixes: 2589726d12 ("bpf: introduce bounded loops") Reported-by: Hao Sun <sunhao.th@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231110061412.2995786-1-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>		2023-11-09 22:57:24 -08:00
..
.gitignore
atomic_and.c
atomic_bounds.c
atomic_cmpxchg.c	selftests/bpf: Add F_NEEDS_EFFICIENT_UNALIGNED_ACCESS to some tests	2023-07-05 14:34:23 +02:00
atomic_fetch.c
atomic_fetch_add.c
atomic_invalid.c
atomic_or.c
atomic_xchg.c
atomic_xor.c
basic.c
basic_call.c
basic_instr.c	selftests/bpf: Fix a test_verifier failure	2023-07-27 18:54:16 -07:00
basic_stx_ldx.c
bpf_loop_inline.c	selftests/bpf: Fix test_verifier failed test in unprivileged mode	2022-07-21 21:03:25 -07:00
bpf_st_mem.c	selftests/bpf: Add test for immediate spilled to stack	2023-11-01 22:30:27 -07:00
calls.c	bpf: fix control-flow graph checking in privileged mode	2023-11-09 22:57:24 -08:00
ctx_sk_lookup.c
ctx_skb.c	selftests/bpf: Add F_NEEDS_EFFICIENT_UNALIGNED_ACCESS to some tests	2023-07-05 14:34:23 +02:00
dead_code.c
direct_value_access.c
event_output.c
jit.c	bpf: add selftests for lsh, rsh, arsh with reg operand	2022-10-19 16:53:51 -07:00
jmp32.c	selftests/bpf: Add F_NEEDS_EFFICIENT_UNALIGNED_ACCESS to some tests	2023-07-05 14:34:23 +02:00
jset.c
jump.c	bpf, selftests: Add verifier test case for imm=0,umin=0,umax=1 scalar	2022-07-01 12:56:27 -07:00
junk_insn.c
ld_abs.c
ld_dw.c
ld_imm64.c	bpf: handle ldimm64 properly in check_cfg()	2023-11-09 20:11:20 -08:00
map_kptr.c	selftests/bpf: Add F_NEEDS_EFFICIENT_UNALIGNED_ACCESS to some tests	2023-07-05 14:34:23 +02:00
perf_event_sample_period.c
precise.c	selftests/bpf: Add F_NEEDS_EFFICIENT_UNALIGNED_ACCESS to some tests	2023-07-05 14:34:23 +02:00
scale.c
sleepable.c	bpf: Allow BPF_PROG_TYPE_STRUCT_OPS programs to be sleepable	2023-01-25 10:25:57 -08:00
wide_access.c