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bpf: Fix atomic probe zero-extension

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Zero-extending results of atomic probe operations fails with:

    verifier bug. zext_dst is set, but no reg is defined

The problem is that insn_def_regno() handles BPF_ATOMICs, but not
BPF_PROBE_ATOMICs. Fix by adding the missing condition.

Fixes: d503a04f8b ("bpf: Add support for certain atomics in bpf_arena to x86 JIT")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240701234304.14336-2-iii@linux.ibm.com
This commit is contained in:
Ilya Leoshkevich 2024-07-02 01:40:19 +02:00 committed by Daniel Borkmann
parent da5f8fd1f0
commit df34ec9db6
1 changed files with 2 additions and 1 deletions
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3
kernel/bpf/verifier.c
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@ -3217,7 +3217,8 @@ static int insn_def_regno(const struct bpf_insn *insn)
case BPF_ST:
return -1;
case BPF_STX:
if (BPF_MODE(insn->code) == BPF_ATOMIC &&
if ((BPF_MODE(insn->code) == BPF_ATOMIC ||
BPF_MODE(insn->code) == BPF_PROBE_ATOMIC) &&
(insn->imm & BPF_FETCH)) {
if (insn->imm == BPF_CMPXCHG)
return BPF_REG_0;