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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 5.11 22/31] bpf: Simplify alu_limit masking for pointer arithmetic
Date: Fri, 19 Mar 2021 13:19:16 +0100	[thread overview]
Message-ID: <20210319121747.917749865@linuxfoundation.org> (raw)
In-Reply-To: <20210319121747.203523570@linuxfoundation.org>

From: Piotr Krysiuk <piotras@gmail.com>

commit b5871dca250cd391885218b99cc015aca1a51aea upstream.

Instead of having the mov32 with aux->alu_limit - 1 immediate, move this
operation to retrieve_ptr_limit() instead to simplify the logic and to
allow for subsequent sanity boundary checks inside retrieve_ptr_limit().
This avoids in future that at the time of the verifier masking rewrite
we'd run into an underflow which would not sign extend due to the nature
of mov32 instruction.

Signed-off-by: Piotr Krysiuk <piotras@gmail.com>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/bpf/verifier.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5398,16 +5398,16 @@ static int retrieve_ptr_limit(const stru
 		 */
 		off = ptr_reg->off + ptr_reg->var_off.value;
 		if (mask_to_left)
-			*ptr_limit = MAX_BPF_STACK + off + 1;
+			*ptr_limit = MAX_BPF_STACK + off;
 		else
-			*ptr_limit = -off;
+			*ptr_limit = -off - 1;
 		return 0;
 	case PTR_TO_MAP_VALUE:
 		if (mask_to_left) {
-			*ptr_limit = ptr_reg->umax_value + ptr_reg->off + 1;
+			*ptr_limit = ptr_reg->umax_value + ptr_reg->off;
 		} else {
 			off = ptr_reg->smin_value + ptr_reg->off;
-			*ptr_limit = ptr_reg->map_ptr->value_size - off;
+			*ptr_limit = ptr_reg->map_ptr->value_size - off - 1;
 		}
 		return 0;
 	default:
@@ -11083,7 +11083,7 @@ static int fixup_bpf_calls(struct bpf_ve
 			off_reg = issrc ? insn->src_reg : insn->dst_reg;
 			if (isneg)
 				*patch++ = BPF_ALU64_IMM(BPF_MUL, off_reg, -1);
-			*patch++ = BPF_MOV32_IMM(BPF_REG_AX, aux->alu_limit - 1);
+			*patch++ = BPF_MOV32_IMM(BPF_REG_AX, aux->alu_limit);
 			*patch++ = BPF_ALU64_REG(BPF_SUB, BPF_REG_AX, off_reg);
 			*patch++ = BPF_ALU64_REG(BPF_OR, BPF_REG_AX, off_reg);
 			*patch++ = BPF_ALU64_IMM(BPF_NEG, BPF_REG_AX, 0);



  parent reply	other threads:[~2021-03-19 12:22 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-19 12:18 [PATCH 5.11 00/31] 5.11.8-rc1 review Greg Kroah-Hartman
2021-03-19 12:18 ` [PATCH 5.11 01/31] io_uring: dont attempt IO reissue from the ring exit path Greg Kroah-Hartman
2021-03-19 12:18 ` [PATCH 5.11 02/31] KVM: x86/mmu: Expand on the comment in kvm_vcpu_ad_need_write_protect() Greg Kroah-Hartman
2021-03-19 12:18 ` [PATCH 5.11 03/31] KVM: x86/mmu: Set SPTE_AD_WRPROT_ONLY_MASK if and only if PML is enabled Greg Kroah-Hartman
2021-03-19 12:18 ` [PATCH 5.11 04/31] mptcp: send ack for every add_addr Greg Kroah-Hartman
2021-03-19 12:18 ` [PATCH 5.11 05/31] mptcp: pm: add lockdep assertions Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 06/31] mptcp: dispose initial struct socket when its subflow is closed Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 07/31] io_uring: refactor scheduling in io_cqring_wait Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 08/31] io_uring: refactor io_cqring_wait Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 09/31] io_uring: dont keep looping for more events if we cant flush overflow Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 10/31] io_uring: simplify do_read return parsing Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 11/31] io_uring: clear IOCB_WAITQ for non -EIOCBQUEUED return Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 12/31] gpiolib: Read "gpio-line-names" from a firmware node Greg Kroah-Hartman
2021-03-19 12:27   ` Marek Vasut
2021-03-19 12:36     ` Greg Kroah-Hartman
2021-03-19 12:45       ` Marek Vasut
2021-03-19 12:19 ` [PATCH 5.11 13/31] net: bonding: fix error return code of bond_neigh_init() Greg Kroah-Hartman
2021-03-19 14:12   ` Jiri Kosina
2021-03-19 14:24     ` Jiri Kosina
2021-03-19 14:29       ` Greg Kroah-Hartman
2021-03-19 14:25     ` Greg Kroah-Hartman
2021-03-19 15:14       ` Jiri Kosina
2021-03-19 12:19 ` [PATCH 5.11 14/31] regulator: pca9450: Add SD_VSEL GPIO for LDO5 Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 15/31] regulator: pca9450: Enable system reset on WDOG_B assertion Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 16/31] regulator: pca9450: Clear PRESET_EN bit to fix BUCK1/2/3 voltage setting Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 17/31] gfs2: Add common helper for holding and releasing the freeze glock Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 18/31] gfs2: move freeze glock outside the make_fs_rw and _ro functions Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 19/31] gfs2: bypass signal_our_withdraw if no journal Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 20/31] bpf: Prohibit alu ops for pointer types not defining ptr_limit Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 21/31] bpf: Fix off-by-one for area size in creating mask to left Greg Kroah-Hartman
2021-03-19 12:19 ` Greg Kroah-Hartman [this message]
2021-03-19 12:19 ` [PATCH 5.11 23/31] bpf: Add sanity check for upper ptr_limit Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 24/31] bpf, selftests: Fix up some test_verifier cases for unprivileged Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 25/31] arm64: Unconditionally set virtual cpu id registers Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 26/31] RDMA/srp: Fix support for unpopulated and unbalanced NUMA nodes Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 27/31] fuse: fix live lock in fuse_iget() Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 28/31] Revert "nfsd4: remove check_conflicting_opens warning" Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 29/31] Revert "nfsd4: a clients own opens neednt prevent delegations" Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 30/31] net: dsa: b53: Support setting learning on port Greg Kroah-Hartman
2021-03-19 12:19 ` [PATCH 5.11 31/31] crypto: x86/aes-ni-xts - use direct calls to and 4-way stride Greg Kroah-Hartman
2021-03-19 19:38 ` [PATCH 5.11 00/31] 5.11.8-rc1 review Naresh Kamboju
2021-03-20  9:52   ` Greg Kroah-Hartman
2021-03-19 21:23 ` Guenter Roeck

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