selftests/bpf: Add tests with stack ptr register in conditional jmp

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

2 files changed, 58 insertions, 2 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 98c52829936e..a7d6e0c5928b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -16456,6 +16456,8 @@ 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");
@@ -16465,10 +16467,11 @@ 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 2dd0d15c2678..9fe5d255ee37 100644
--- a/tools/testing/selftests/bpf/progs/verifier_precision.c
+++ b/tools/testing/selftests/bpf/progs/verifier_precision.c
@@ -178,4 +178,57 @@ __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";