From: Kurt Manucredo <fuzzybritches0@gmail.com>
To: syzbot+bed360704c521841c85d@syzkaller.appspotmail.com
Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, davem@davemloft.net, hawk@kernel.org,
john.fastabend@gmail.com, kafai@fb.com, kpsingh@kernel.org,
kuba@kernel.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, songliubraving@fb.com,
syzkaller-bugs@googlegroups.com, yhs@fb.com, nathan@kernel.org,
ndesaulniers@google.com, clang-built-linux@googlegroups.com,
linux-kernel-mentees@lists.linuxfoundation.org,
skhan@linuxfoundation.org, gregkh@linuxfoundation.org,
Kurt Manucredo <fuzzybritches0@gmail.com>
Subject: [PATCH v4] bpf: core: fix shift-out-of-bounds in ___bpf_prog_run
Date: Sat, 5 Jun 2021 15:01:57 +0000 [thread overview]
Message-ID: <87609-531187-curtm@phaethon> (raw)
In-Reply-To: <YLhd8BL3HGItbXmx@kroah.com>
Syzbot detects a shift-out-of-bounds in ___bpf_prog_run()
kernel/bpf/core.c:1414:2.
I propose: In adjust_scalar_min_max_vals() move boundary check up to avoid
missing them and return with error when detected.
Reported-and-tested-by: syzbot+bed360704c521841c85d@syzkaller.appspotmail.com
Signed-off-by: Kurt Manucredo <fuzzybritches0@gmail.com>
---
https://syzkaller.appspot.com/bug?id=edb51be4c9a320186328893287bb30d5eed09231
Changelog:
----------
v4 - Fix shift-out-of-bounds in adjust_scalar_min_max_vals.
Fix commit message.
v3 - Make it clearer what the fix is for.
v2 - Fix shift-out-of-bounds in ___bpf_prog_run() by adding boundary
check in check_alu_op() in verifier.c.
v1 - Fix shift-out-of-bounds in ___bpf_prog_run() by adding boundary
check in ___bpf_prog_run().
thanks
kind regards
Kurt
kernel/bpf/verifier.c | 30 +++++++++---------------------
1 file changed, 9 insertions(+), 21 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 94ba5163d4c5..ed0eecf20de5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7510,6 +7510,15 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
u32_min_val = src_reg.u32_min_value;
u32_max_val = src_reg.u32_max_value;
+ if ((opcode == BPF_LSH || opcode == BPF_RSH || opcode == BPF_ARSH) &&
+ umax_val >= insn_bitness) {
+ /* Shifts greater than 31 or 63 are undefined.
+ * This includes shifts by a negative number.
+ */
+ verbose(env, "invalid shift %lld\n", umax_val);
+ return -EINVAL;
+ }
+
if (alu32) {
src_known = tnum_subreg_is_const(src_reg.var_off);
if ((src_known &&
@@ -7592,39 +7601,18 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
scalar_min_max_xor(dst_reg, &src_reg);
break;
case BPF_LSH:
- if (umax_val >= insn_bitness) {
- /* Shifts greater than 31 or 63 are undefined.
- * This includes shifts by a negative number.
- */
- mark_reg_unknown(env, regs, insn->dst_reg);
- break;
- }
if (alu32)
scalar32_min_max_lsh(dst_reg, &src_reg);
else
scalar_min_max_lsh(dst_reg, &src_reg);
break;
case BPF_RSH:
- if (umax_val >= insn_bitness) {
- /* Shifts greater than 31 or 63 are undefined.
- * This includes shifts by a negative number.
- */
- mark_reg_unknown(env, regs, insn->dst_reg);
- break;
- }
if (alu32)
scalar32_min_max_rsh(dst_reg, &src_reg);
else
scalar_min_max_rsh(dst_reg, &src_reg);
break;
case BPF_ARSH:
- if (umax_val >= insn_bitness) {
- /* Shifts greater than 31 or 63 are undefined.
- * This includes shifts by a negative number.
- */
- mark_reg_unknown(env, regs, insn->dst_reg);
- break;
- }
if (alu32)
scalar32_min_max_arsh(dst_reg, &src_reg);
else
--
2.30.2
next prev parent reply other threads:[~2021-06-05 15:02 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-10 16:05 [syzbot] UBSAN: shift-out-of-bounds in ___bpf_prog_run syzbot
2021-03-28 3:38 ` syzbot
2021-06-02 21:27 ` [PATCH v3] bpf: core: fix " Kurt Manucredo
2021-06-03 4:43 ` Greg KH
2021-06-05 15:01 ` Kurt Manucredo [this message]
2021-06-05 17:55 ` [PATCH v4] " Yonghong Song
2021-06-05 19:10 ` Alexei Starovoitov
2021-06-05 21:39 ` Yonghong Song
2021-06-06 19:44 ` Kurt Manucredo
2021-06-07 7:38 ` Dmitry Vyukov
2021-06-09 18:20 ` Kees Cook
2021-06-09 23:40 ` Yonghong Song
2021-06-10 5:32 ` Dmitry Vyukov
2021-06-10 6:06 ` Yonghong Song
2021-06-10 17:06 ` Kees Cook
2021-06-10 17:52 ` Alexei Starovoitov
2021-06-10 20:00 ` Eric Biggers
2021-06-15 16:42 ` [PATCH v5] " Kurt Manucredo
2021-06-15 18:51 ` Edward Cree
2021-06-15 19:33 ` Eric Biggers
2021-06-15 21:08 ` Daniel Borkmann
2021-06-15 21:32 ` Eric Biggers
2021-06-15 21:38 ` Eric Biggers
2021-06-15 21:54 ` Daniel Borkmann
2021-06-15 22:07 ` Eric Biggers
2021-06-15 22:31 ` Kurt Manucredo
2021-06-17 10:09 ` Daniel Borkmann
2021-06-06 19:15 ` [PATCH v4] " Kurt Manucredo
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