| Message ID | 20210812140518.183178-2-iii@linux.ibm.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: clear zext_dst of dead insns | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | fail | 2 blamed authors not CCed: jiong.wang@netronome.com kuba@kernel.org; 9 maintainers not CCed: netdev@vger.kernel.org andrii@kernel.org john.fastabend@gmail.com kuba@kernel.org songliubraving@fb.com yhs@fb.com jiong.wang@netronome.com kpsingh@kernel.org kafai@fb.com |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 30 this patch: 30 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 7 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 30 this patch: 30 |
| netdev/header_inline | success | Link |
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index f9bda5476ea5..381d3d6f24bc 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11663,6 +11663,7 @@ static void sanitize_dead_code(struct bpf_verifier_env *env) if (aux_data[i].seen) continue; memcpy(insn + i, &trap, sizeof(trap)); + aux_data[i].zext_dst = false; } }
"access skb fields ok" verifier test fails on s390 with the "verifier bug. zext_dst is set, but no reg is defined" message. The first insns of the test prog are: 0: 61 01 00 00 00 00 00 00 ldxw %r0,[%r1+0] 8: 35 00 00 01 00 00 00 00 jge %r0,0,1 10: 61 01 00 08 00 00 00 00 ldxw %r0,[%r1+8] and the 3rd one is dead (this does not look intentional to me, but this is a separate topic). sanitize_dead_code() converts dead insns into "ja -1", but keeps zext_dst. When opt_subreg_zext_lo32_rnd_hi32() tries to parse such an insn, it sees this discrepancy and bails. This problem can be seen only with JITs whose bpf_jit_needs_zext() returns true. Fix by clearning dead insns' zext_dst. The commits that contributed to this problem are: 1. commit 5aa5bd14c5f8 ("bpf: add initial suite for selftests"), which introduced the test with the dead code. 2. commit 5327ed3d44b7 ("bpf: verifier: mark verified-insn with sub-register zext flag"), which introduced the zext_dst flag. 3. commit 83a2881903f3 ("bpf: Account for BPF_FETCH in insn_has_def32()"), which introduced the sanity check. 4. commit 9183671af6db ("bpf: Fix leakage under speculation on mispredicted branches"), which bisect points to. It's best to fix this on stable branches that contain the second one, since that's the point where the inconsistency was introduced. Fixes: 5327ed3d44b7 ("bpf: verifier: mark verified-insn with sub-register zext flag") Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- kernel/bpf/verifier.c | 1 + 1 file changed, 1 insertion(+)