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bpf: Fix tnum_overlap to check for zero mask intersection #6237

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bpf: Fix tnum_overlap to check for zero mask intersection #6237

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d6dbee3
bpf: Fix tnum_overlap to check for zero mask intersection
mannkafai Oct 28, 2025
ab6f527
selftests/bpf: Range analysis test case for JEQ
mannkafai Oct 28, 2025
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2 changes: 2 additions & 0 deletions kernel/bpf/tnum.c
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Original file line number Diff line number Diff line change
Expand Up @@ -163,6 +163,8 @@ bool tnum_overlap(struct tnum a, struct tnum b)
{
u64 mu;

if (a.mask && b.mask && !(a.mask & b.mask))
return false;
mu = ~a.mask & ~b.mask;
return (a.value & mu) == (b.value & mu);
}
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23 changes: 23 additions & 0 deletions tools/testing/selftests/bpf/progs/verifier_bounds.c
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Expand Up @@ -1550,6 +1550,29 @@ l0_%=: r0 = 0; \
: __clobber_all);
}

SEC("socket")
__description("dead branch on jeq, does not result in invariants violation error")
__success __log_level(2)
__retval(0) __flag(BPF_F_TEST_REG_INVARIANTS)
__naked void jeq_range_analysis(void)
{
asm volatile (" \
call %[bpf_get_prandom_u32]; \
r6 = r0; \
r6 &= 0xFFFFFFFFFFFFFFF0; \
r7 = r0; \
r7 &= 0x07; \
r7 -= 0xFF; \
if r6 == r7 goto l1_%=; \
l0_%=: r0 = 0; \
exit; \
l1_%=: r0 = 1; \
exit; \
" :
: __imm(bpf_get_prandom_u32)
: __clobber_all);
}

/* This test covers the bounds deduction on 64bits when the s64 and u64 ranges
* overlap on the negative side. At instruction 7, the ranges look as follows:
*
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