4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Alexei Starovoitov <ast@xxxxxxxxxx>
[ upstream commit 68fda450a7df51cff9e5a4d4a4d9d0d5f2589153 ]
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/bpf/verifier.c | 18 ++++++++++++++++++
net/core/filter.c | 4 ++++
2 files changed, 22 insertions(+)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3391,6 +3391,24 @@ static int fixup_bpf_calls(struct bpf_ve
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;
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -441,6 +441,10 @@ do_pass:
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;