diff options
| author | Ilya Leoshkevich <iii@linux.ibm.com> | 2023-09-19 12:09:03 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-09-21 14:21:59 -0700 |
| commit | 577c06af8188d1f6919ef7b62fc1b78fb1b86eb7 (patch) | |
| tree | a0d8ec9578e9a9393baf2163d95cffa01590d790 | |
| parent | e9cbc89067cce78211c8629c78e931c0fe64e29d (diff) | |
bpf: Disable zero-extension for BPF_MEMSX
On the architectures that use bpf_jit_needs_zext(), e.g., s390x, the
verifier incorrectly inserts a zero-extension after BPF_MEMSX, leading
to miscompilations like the one below:
24: 89 1a ff fe 00 00 00 00 "r1 = *(s16 *)(r10 - 2);" # zext_dst set
0x3ff7fdb910e: lgh %r2,-2(%r13,%r0) # load halfword
0x3ff7fdb9114: llgfr %r2,%r2 # wrong!
25: 65 10 00 03 00 00 7f ff if r1 s> 32767 goto +3 <l0_1> # check_cond_jmp_op()
Disable such zero-extensions. The JITs need to insert sign-extension
themselves, if necessary.
Suggested-by: Puranjay Mohan <puranjay12@gmail.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Puranjay Mohan <puranjay12@gmail.com>
Link: https://lore.kernel.org/r/20230919101336.2223655-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | kernel/bpf/verifier.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 38f8718f1602..eed7350e15f4 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3114,7 +3114,7 @@ static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn, if (class == BPF_LDX) { if (t != SRC_OP) - return BPF_SIZE(code) == BPF_DW; + return BPF_SIZE(code) == BPF_DW || BPF_MODE(code) == BPF_MEMSX; /* LDX source must be ptr. */ return true; } |