From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Piotr Krysiuk <piotras@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>
Subject: [PATCH 5.12 2/7] bpf: Fix mask direction swap upon off reg sign change
Date: Thu, 27 May 2021 17:13:03 +0200 [thread overview]
Message-ID: <20210527151139.325778980@linuxfoundation.org> (raw)
In-Reply-To: <20210527151139.241267495@linuxfoundation.org>
From: Daniel Borkmann <daniel@iogearbox.net>
commit bb01a1bba579b4b1c5566af24d95f1767859771e upstream.
Masking direction as indicated via mask_to_left is considered to be
calculated once and then used to derive pointer limits. Thus, this
needs to be placed into bpf_sanitize_info instead so we can pass it
to sanitize_ptr_alu() call after the pointer move. Piotr noticed a
corner case where the off reg causes masking direction change which
then results in an incorrect final aux->alu_limit.
Fixes: 7fedb63a8307 ("bpf: Tighten speculative pointer arithmetic mask")
Reported-by: Piotr Krysiuk <piotras@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Piotr Krysiuk <piotras@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/verifier.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5863,18 +5863,10 @@ enum {
};
static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
- const struct bpf_reg_state *off_reg,
- u32 *alu_limit, u8 opcode)
+ u32 *alu_limit, bool mask_to_left)
{
- bool off_is_neg = off_reg->smin_value < 0;
- bool mask_to_left = (opcode == BPF_ADD && off_is_neg) ||
- (opcode == BPF_SUB && !off_is_neg);
u32 max = 0, ptr_limit = 0;
- if (!tnum_is_const(off_reg->var_off) &&
- (off_reg->smin_value < 0) != (off_reg->smax_value < 0))
- return REASON_BOUNDS;
-
switch (ptr_reg->type) {
case PTR_TO_STACK:
/* Offset 0 is out-of-bounds, but acceptable start for the
@@ -5942,6 +5934,7 @@ static bool sanitize_needed(u8 opcode)
struct bpf_sanitize_info {
struct bpf_insn_aux_data aux;
+ bool mask_to_left;
};
static int sanitize_ptr_alu(struct bpf_verifier_env *env,
@@ -5973,7 +5966,16 @@ static int sanitize_ptr_alu(struct bpf_v
if (vstate->speculative)
goto do_sim;
- err = retrieve_ptr_limit(ptr_reg, off_reg, &alu_limit, opcode);
+ if (!commit_window) {
+ if (!tnum_is_const(off_reg->var_off) &&
+ (off_reg->smin_value < 0) != (off_reg->smax_value < 0))
+ return REASON_BOUNDS;
+
+ info->mask_to_left = (opcode == BPF_ADD && off_is_neg) ||
+ (opcode == BPF_SUB && !off_is_neg);
+ }
+
+ err = retrieve_ptr_limit(ptr_reg, &alu_limit, info->mask_to_left);
if (err < 0)
return err;
next prev parent reply other threads:[~2021-05-27 15:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 15:13 [PATCH 5.12 0/7] 5.12.8-rc1 review Greg Kroah-Hartman
2021-05-27 15:13 ` [PATCH 5.12 1/7] bpf: Wrap aux data inside bpf_sanitize_info container Greg Kroah-Hartman
2021-05-27 15:13 ` Greg Kroah-Hartman [this message]
2021-05-27 15:13 ` [PATCH 5.12 3/7] bpf: No need to simulate speculative domain for immediates Greg Kroah-Hartman
2021-05-27 15:13 ` [PATCH 5.12 4/7] context_tracking: Move guest exit context tracking to separate helpers Greg Kroah-Hartman
2021-05-27 15:13 ` [PATCH 5.12 5/7] context_tracking: Move guest exit vtime accounting " Greg Kroah-Hartman
2021-05-27 15:13 ` [PATCH 5.12 6/7] KVM: x86: Defer vtime accounting til after IRQ handling Greg Kroah-Hartman
2021-05-27 15:13 ` [PATCH 5.12 7/7] NFC: nci: fix memory leak in nci_allocate_device Greg Kroah-Hartman
2021-05-27 22:28 ` [PATCH 5.12 0/7] 5.12.8-rc1 review Fox Chen
2021-05-28 0:00 ` Shuah Khan
2021-05-28 3:34 ` Florian Fainelli
2021-05-28 6:00 ` Guenter Roeck
2021-05-28 6:04 ` Naresh Kamboju
2021-05-28 12:15 ` Rudi Heitbaum
2021-05-28 13:53 ` Justin Forbes
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