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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Piotr Krysiuk <piotras@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>
Subject: [PATCH 4.14 43/47] bpf: No need to simulate speculative domain for immediates
Date: Tue,  8 Jun 2021 20:27:26 +0200
Message-ID: <20210608175931.905528105@linuxfoundation.org> (raw)
In-Reply-To: <20210608175930.477274100@linuxfoundation.org>

From: Daniel Borkmann <daniel@iogearbox.net>

commit a7036191277f9fa68d92f2071ddc38c09b1e5ee5 upstream.

In 801c6058d14a ("bpf: Fix leakage of uninitialized bpf stack under
speculation") we replaced masking logic with direct loads of immediates
if the register is a known constant. Given in this case we do not apply
any masking, there is also no reason for the operation to be truncated
under the speculative domain.

Therefore, there is also zero reason for the verifier to branch-off and
simulate this case, it only needs to do it for unknown but bounded scalars.
As a side-effect, this also enables few test cases that were previously
rejected due to simulation under zero truncation.

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 |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2169,8 +2169,12 @@ do_sim:
 	/* If we're in commit phase, we're done here given we already
 	 * pushed the truncated dst_reg into the speculative verification
 	 * stack.
+	 *
+	 * Also, when register is a known constant, we rewrite register-based
+	 * operation to immediate-based, and thus do not need masking (and as
+	 * a consequence, do not need to simulate the zero-truncation either).
 	 */
-	if (commit_window)
+	if (commit_window || off_is_imm)
 		return 0;
 
 	/* Simulate and find potential out-of-bounds access under



  parent reply index

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-08 18:26 [PATCH 4.14 00/47] 4.14.236-rc1 review Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 01/47] net: usb: cdc_ncm: dont spew notifications Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 02/47] efi: Allow EFI_MEMORY_XP and EFI_MEMORY_RO both to be cleared Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 03/47] efi: cper: fix snprintf() use in cper_dimm_err_location() Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 04/47] vfio/pci: Fix error return code in vfio_ecap_init() Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 05/47] vfio/pci: zap_vma_ptes() needs MMU Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 06/47] vfio/platform: fix module_put call in error flow Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 07/47] ipvs: ignore IP_VS_SVC_F_HASHED flag when adding service Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 08/47] HID: pidff: fix error return code in hid_pidff_init() Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 09/47] HID: i2c-hid: fix format string mismatch Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 10/47] netfilter: nfnetlink_cthelper: hit EBUSY on updates if size mismatches Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 11/47] ieee802154: fix error return code in ieee802154_add_iface() Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 12/47] ieee802154: fix error return code in ieee802154_llsec_getparams() Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 13/47] Bluetooth: fix the erroneous flush_work() order Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 14/47] Bluetooth: use correct lock to prevent UAF of hdev object Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 15/47] net: caif: added cfserl_release function Greg Kroah-Hartman
2021-06-08 18:26 ` [PATCH 4.14 16/47] net: caif: add proper error handling Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 17/47] net: caif: fix memory leak in caif_device_notify Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 18/47] net: caif: fix memory leak in cfusbl_device_notify Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 19/47] ALSA: timer: Fix master timer notification Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 20/47] ext4: fix bug on in ext4_es_cache_extent as ext4_split_extent_at failed Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 21/47] pid: take a reference when initializing `cad_pid` Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 22/47] ocfs2: fix data corruption by fallocate Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 23/47] nfc: fix NULL ptr dereference in llcp_sock_getname() after failed connect Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 24/47] btrfs: fix error handling in btrfs_del_csums Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 25/47] btrfs: fixup error handling in fixup_inode_link_counts Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 26/47] mm, hugetlb: fix simple resv_huge_pages underflow on UFFDIO_COPY Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 27/47] bpf, selftests: Fix up some test_verifier cases for unprivileged Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 28/47] bpf: Move off_reg into sanitize_ptr_alu Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 29/47] bpf: Ensure off_reg has no mixed signed bounds for all types Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 30/47] bpf: Rework ptr_limit into alu_limit and add common error path Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 31/47] bpf: Improve verifier error messages for users Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 32/47] bpf: Refactor and streamline bounds check into helper Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 33/47] bpf: Move sanitize_val_alu out of op switch Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 34/47] bpf: Tighten speculative pointer arithmetic mask Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 35/47] bpf: Update selftests to reflect new error states Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 36/47] bpf: do not allow root to mangle valid pointers Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 37/47] bpf/verifier: disallow pointer subtraction Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 38/47] selftests/bpf: fix test_align Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 39/47] selftests/bpf: make dubious pointer arithmetic test useful Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 40/47] bpf: Fix leakage of uninitialized bpf stack under speculation Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 41/47] bpf: Wrap aux data inside bpf_sanitize_info container Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 42/47] bpf: Fix mask direction swap upon off reg sign change Greg Kroah-Hartman
2021-06-08 18:27 ` Greg Kroah-Hartman [this message]
2021-06-08 18:27 ` [PATCH 4.14 44/47] bnxt_en: Remove the setting of dev_port Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 45/47] KVM: SVM: Truncate GPR value for DR and CR accesses in !64-bit mode Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 46/47] sched/fair: Optimize select_idle_cpu Greg Kroah-Hartman
2021-06-08 18:27 ` [PATCH 4.14 47/47] xen-pciback: redo VF placement in the virtual topology Greg Kroah-Hartman
2021-06-09  9:33 ` [PATCH 4.14 00/47] 4.14.236-rc1 review Jon Hunter
2021-06-09 11:25 ` Naresh Kamboju
2021-06-09 18:48 ` Guenter Roeck

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