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bpf: Skip bounds adjustment for conditional jumps on same register #10072

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bpf: Skip bounds adjustment for conditional jumps on same register #10072

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a559c56
bpf: Skip bounds adjustment for conditional jumps on same register
mannkafai Oct 22, 2025
2d57453
selftests/bpf: Add test for conditional jumps on same register
mannkafai Oct 22, 2025
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4 changes: 4 additions & 0 deletions kernel/bpf/verifier.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16429,6 +16429,10 @@ static int reg_set_min_max(struct bpf_verifier_env *env,
if (false_reg1->type != SCALAR_VALUE || false_reg2->type != SCALAR_VALUE)
return 0;

/* If conditional jumps on the same register, skip the adjustment */
if (false_reg1 == false_reg2)
return 0;

/* fallthrough (FALSE) branch */
regs_refine_cond_op(false_reg1, false_reg2, rev_opcode(opcode), is_jmp32);
reg_bounds_sync(false_reg1);
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17 changes: 17 additions & 0 deletions tools/testing/selftests/bpf/progs/verifier_bounds.c
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Expand Up @@ -1709,4 +1709,21 @@ __naked void jeq_disagreeing_tnums(void *ctx)
: __clobber_all);
}

SEC("socket")
__description("JGT on same register")
__success __log_level(2)
__naked void jgt_same_register(void *ctx)
{
asm volatile(" \
call %[bpf_get_prandom_u32]; \
w8 = 0x80000000; \
r0 &= r8; \
if r0 > r0 goto +1; \
call %[bpf_get_prandom_u32]; \
exit; \
" :
: __imm(bpf_get_prandom_u32)
: __clobber_all);
}

char _license[] SEC("license") = "GPL";
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