From: Ovidiu Panait <ovidiu.panait@windriver.com>
To: stable@vger.kernel.org
Cc: fllinden@amazon.com, bpf@vger.kernel.org, ast@kernel.org,
daniel@iogearbox.net, yhs@fb.com, john.fastabend@gmail.com,
samjonas@amazon.com
Subject: [PATCH 4.19 06/12] bpf: Ensure off_reg has no mixed signed bounds for all types
Date: Thu, 27 May 2021 20:37:26 +0300 [thread overview]
Message-ID: <20210527173732.20860-7-ovidiu.panait@windriver.com> (raw)
In-Reply-To: <20210527173732.20860-1-ovidiu.panait@windriver.com>
From: Daniel Borkmann <daniel@iogearbox.net>
commit 24c109bb1537c12c02aeed2d51a347b4d6a9b76e upstream.
The mixed signed bounds check really belongs into retrieve_ptr_limit()
instead of outside of it in adjust_ptr_min_max_vals(). The reason is
that this check is not tied to PTR_TO_MAP_VALUE only, but to all pointer
types that we handle in retrieve_ptr_limit() and given errors from the latter
propagate back to adjust_ptr_min_max_vals() and lead to rejection of the
program, it's a better place to reside to avoid anything slipping through
for future types. The reason why we must reject such off_reg is that we
otherwise would not be able to derive a mask, see details in 9d7eceede769
("bpf: restrict unknown scalars of mixed signed bounds for unprivileged").
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
[fllinden@amazon.com: backport to 5.4]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[OP: backport to 4.19]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
---
kernel/bpf/verifier.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5e0646efac6d..b260bcc7215f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2730,12 +2730,18 @@ static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env)
}
static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
- u32 *ptr_limit, u8 opcode, bool off_is_neg)
+ const struct bpf_reg_state *off_reg,
+ u32 *ptr_limit, u8 opcode)
{
+ 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 off, max;
+ if (!tnum_is_const(off_reg->var_off) &&
+ (off_reg->smin_value < 0) != (off_reg->smax_value < 0))
+ return -EACCES;
+
switch (ptr_reg->type) {
case PTR_TO_STACK:
/* Offset 0 is out-of-bounds, but acceptable start for the
@@ -2826,7 +2832,7 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env,
alu_state |= ptr_is_dst_reg ?
BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST;
- err = retrieve_ptr_limit(ptr_reg, &alu_limit, opcode, off_is_neg);
+ err = retrieve_ptr_limit(ptr_reg, off_reg, &alu_limit, opcode);
if (err < 0)
return err;
@@ -2871,8 +2877,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value;
u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value,
umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value;
- u32 dst = insn->dst_reg, src = insn->src_reg;
u8 opcode = BPF_OP(insn->code);
+ u32 dst = insn->dst_reg;
int ret;
dst_reg = ®s[dst];
@@ -2909,12 +2915,6 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
dst);
return -EACCES;
}
- if (ptr_reg->type == PTR_TO_MAP_VALUE &&
- !env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) {
- verbose(env, "R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n",
- off_reg == dst_reg ? dst : src);
- return -EACCES;
- }
/* In case of 'scalar += pointer', dst_reg inherits pointer type and id.
* The id may be overwritten later if we create a new variable offset.
--
2.17.1
next prev parent reply other threads:[~2021-05-27 17:38 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 17:37 [PATCH 4.19 00/12] bpf: fix verifier selftests, add CVE-2021-29155 fixes Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 01/12] bpf: fix up selftests after backports were fixed Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 02/12] bpf, selftests: Fix up some test_verifier cases for unprivileged Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 03/12] selftests/bpf: Test narrow loads with off > 0 in test_verifier Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 04/12] selftests/bpf: add selftest part of "bpf: improve verifier branch analysis" Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 05/12] bpf: Move off_reg into sanitize_ptr_alu Ovidiu Panait
2021-05-27 17:37 ` Ovidiu Panait [this message]
2021-05-27 17:37 ` [PATCH 4.19 07/12] bpf: Rework ptr_limit into alu_limit and add common error path Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 08/12] bpf: Improve verifier error messages for users Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 09/12] bpf: Refactor and streamline bounds check into helper Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 10/12] bpf: Move sanitize_val_alu out of op switch Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 11/12] bpf: Tighten speculative pointer arithmetic mask Ovidiu Panait
2021-05-27 17:37 ` [PATCH 4.19 12/12] bpf: Update selftests to reflect new error states Ovidiu Panait
2021-05-27 19:44 ` [PATCH 4.19 00/12] bpf: fix verifier selftests, add CVE-2021-29155 fixes Daniel Borkmann
2021-05-27 20:31 ` Frank van der Linden
2021-05-28 10:12 ` Tiezhu Yang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210527173732.20860-7-ovidiu.panait@windriver.com \
--to=ovidiu.panait@windriver.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=fllinden@amazon.com \
--cc=john.fastabend@gmail.com \
--cc=samjonas@amazon.com \
--cc=stable@vger.kernel.org \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).