From: Yonghong Song yonghong.song@linux.dev

Commit 5ffb537e416ee22dbfb3d552102e50da33fec7f6 upstream.

Add two tests: - one test has 'rX <op> r10' where rX is not r10, and - another test has 'rX <op> rY' where rX and rY are not r10 but there is an early insn 'rX = r10'.

Without previous verifier change, both tests will fail.

Signed-off-by: Yonghong Song yonghong.song@linux.dev Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20250524041340.4046304-1-yonghong.song@linux.dev [ shung-hsi.yu: contains additional hunks for kernel/bpf/verifier.c that should be part of the previous patch in the series, commit e2d2115e56c4 "bpf: Do not include stack ptr register in precision backtracking bookkeeping", which already incorporated. ] Link: https://lore.kernel.org/all/9b41f9f5-396f-47e0-9a12-46c52087df6c@linux.dev/ Signed-off-by: Shung-Hsi Yu shung-hsi.yu@suse.com --- Verified that newly added test passes in 6.15.y[1] as well as 6.12.y[2]

1: https://github.com/shunghsiyu/libbpf/actions/runs/16561115937/job/4683091253... 2: https://github.com/shunghsiyu/libbpf/actions/runs/16561115937/job/4683091253... --- kernel/bpf/verifier.c | 7 ++- .../selftests/bpf/progs/verifier_precision.c | 53 +++++++++++++++++++ 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index f01477cecf39..531412c5103d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -15480,6 +15480,8 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,

if (src_reg->type == PTR_TO_STACK) insn_flags |= INSN_F_SRC_REG_STACK; + if (dst_reg->type == PTR_TO_STACK) + insn_flags |= INSN_F_DST_REG_STACK; } else { if (insn->src_reg != BPF_REG_0) { verbose(env, "BPF_JMP/JMP32 uses reserved fields\n"); @@ -15489,10 +15491,11 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, memset(src_reg, 0, sizeof(*src_reg)); src_reg->type = SCALAR_VALUE; __mark_reg_known(src_reg, insn->imm); + + if (dst_reg->type == PTR_TO_STACK) + insn_flags |= INSN_F_DST_REG_STACK; }

- if (dst_reg->type == PTR_TO_STACK) - insn_flags |= INSN_F_DST_REG_STACK; if (insn_flags) { err = push_insn_history(env, this_branch, insn_flags, 0); if (err) diff --git a/tools/testing/selftests/bpf/progs/verifier_precision.c b/tools/testing/selftests/bpf/progs/verifier_precision.c index 6b564d4c0986..051d1962a4c7 100644 --- a/tools/testing/selftests/bpf/progs/verifier_precision.c +++ b/tools/testing/selftests/bpf/progs/verifier_precision.c @@ -130,4 +130,57 @@ __naked int state_loop_first_last_equal(void) ); }

+__used __naked static void __bpf_cond_op_r10(void) +{ + asm volatile ( + "r2 = 2314885393468386424 ll;" + "goto +0;" + "if r2 <= r10 goto +3;" + "if r1 >= -1835016 goto +0;" + "if r2 <= 8 goto +0;" + "if r3 <= 0 goto +0;" + "exit;" + ::: __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("8: (bd) if r2 <= r10 goto pc+3") +__msg("9: (35) if r1 >= 0xffe3fff8 goto pc+0") +__msg("10: (b5) if r2 <= 0x8 goto pc+0") +__msg("mark_precise: frame1: last_idx 10 first_idx 0 subseq_idx -1") +__msg("mark_precise: frame1: regs=r2 stack= before 9: (35) if r1 >= 0xffe3fff8 goto pc+0") +__msg("mark_precise: frame1: regs=r2 stack= before 8: (bd) if r2 <= r10 goto pc+3") +__msg("mark_precise: frame1: regs=r2 stack= before 7: (05) goto pc+0") +__naked void bpf_cond_op_r10(void) +{ + asm volatile ( + "r3 = 0 ll;" + "call __bpf_cond_op_r10;" + "r0 = 0;" + "exit;" + ::: __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("3: (bf) r3 = r10") +__msg("4: (bd) if r3 <= r2 goto pc+1") +__msg("5: (b5) if r2 <= 0x8 goto pc+2") +__msg("mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1") +__msg("mark_precise: frame0: regs=r2 stack= before 4: (bd) if r3 <= r2 goto pc+1") +__msg("mark_precise: frame0: regs=r2 stack= before 3: (bf) r3 = r10") +__naked void bpf_cond_op_not_r10(void) +{ + asm volatile ( + "r0 = 0;" + "r2 = 2314885393468386424 ll;" + "r3 = r10;" + "if r3 <= r2 goto +1;" + "if r2 <= 8 goto +2;" + "r0 = 2 ll;" + "exit;" + ::: __clobber_all); +} + char _license[] SEC("license") = "GPL";