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| author | Alexei Starovoitov <ast@kernel.org> | 2018-01-12 18:59:52 -0800 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-01-14 23:05:33 +0100 |
| commit | 68fda450a7df51cff9e5a4d4a4d9d0d5f2589153 (patch) | |
| tree | 555aa6473c3d960c0a95bd9c4843c8b48947cf1f /kernel/bpf/verifier.c | |
| parent | c366287ebd698ef5e3de300d90cd62ee9ee7373e (diff) | |
| download | lwn-68fda450a7df51cff9e5a4d4a4d9d0d5f2589153.tar.gz lwn-68fda450a7df51cff9e5a4d4a4d9d0d5f2589153.zip | |
bpf: fix 32-bit divide by zero
due to some JITs doing if (src_reg == 0) check in 64-bit mode
for div/mod operations mask upper 32-bits of src register
before doing the check
Fixes: 622582786c9e ("net: filter: x86: internal BPF JIT")
Fixes: 7a12b5031c6b ("sparc64: Add eBPF JIT.")
Reported-by: syzbot+48340bb518e88849e2e3@syzkaller.appspotmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel/bpf/verifier.c')
| -rw-r--r-- | kernel/bpf/verifier.c | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 20eb04fd155e..b7448347e6b6 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4445,6 +4445,24 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) int i, cnt, delta = 0; for (i = 0; i < insn_cnt; i++, insn++) { + if (insn->code == (BPF_ALU | BPF_MOD | BPF_X) || + insn->code == (BPF_ALU | BPF_DIV | BPF_X)) { + /* due to JIT bugs clear upper 32-bits of src register + * before div/mod operation + */ + insn_buf[0] = BPF_MOV32_REG(insn->src_reg, insn->src_reg); + insn_buf[1] = *insn; + cnt = 2; + new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); + if (!new_prog) + return -ENOMEM; + + delta += cnt - 1; + env->prog = prog = new_prog; + insn = new_prog->insnsi + i + delta; + continue; + } + if (insn->code != (BPF_JMP | BPF_CALL)) continue; |