Commit 68fda450 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann

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: 62258278 ("net: filter: x86: internal BPF JIT")
Fixes: 7a12b503 ("sparc64: Add eBPF JIT.")
Reported-by: syzbot+48340bb518e88849e2e3@syzkaller.appspotmail.com
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent c366287e
......@@ -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;
......
......@@ -458,6 +458,10 @@ static int bpf_convert_filter(struct sock_filter *prog, int len,
convert_bpf_extensions(fp, &insn))
break;
if (fp->code == (BPF_ALU | BPF_DIV | BPF_X) ||
fp->code == (BPF_ALU | BPF_MOD | BPF_X))
*insn++ = BPF_MOV32_REG(BPF_REG_X, BPF_REG_X);
*insn = BPF_RAW_INSN(fp->code, BPF_REG_A, BPF_REG_X, 0, fp->k);
break;
......
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