From: Kees Cook <keescook@chromium.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <lenb@kernel.org>,
linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
Nick Desaulniers <ndesaulniers@google.com>,
Sami Tolvanen <samitolvanen@google.com>,
clang-built-linux@googlegroups.com
Subject: Re: [PATCH 1/2] ACPI: bgrt: Fix CFI violation
Date: Wed, 23 Jun 2021 09:32:15 -0700 [thread overview]
Message-ID: <202106230932.198A54C1B8@keescook> (raw)
In-Reply-To: <20210623013802.1904951-1-nathan@kernel.org>
On Tue, Jun 22, 2021 at 06:38:01PM -0700, Nathan Chancellor wrote:
> clang's Control Flow Integrity requires that every indirect call has a
> valid target, which is based on the type of the function pointer. The
> *_show() functions in this file are written as if they will be called
> from dev_attr_show(); however, they will be called from
> sysfs_kf_seq_show() because the files were created by
> sysfs_create_group() and the sysfs ops are based on kobj_sysfs_ops
> because of kobject_add_and_create(). Because the *_show() functions do
> not match the type of the show() member in struct kobj_attribute, there
> is a CFI violation.
>
> $ cat /sys/firmware/acpi/bgrt/{status,type,version,{x,y}offset}}
> 1
> 0
> 1
> 522
> 307
>
> $ dmesg | grep "CFI failure"
> [ 267.761825] CFI failure (target: type_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8):
> [ 267.762246] CFI failure (target: xoffset_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8):
> [ 267.762584] CFI failure (target: status_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8):
> [ 267.762973] CFI failure (target: yoffset_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8):
> [ 267.763330] CFI failure (target: version_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8):
>
> Convert these functions to the type of the show() member in struct
> kobj_attribute so that there is no more CFI violation. Because these
> functions are all so similar, combine them into a macro.
>
> Fixes: d1ff4b1cdbab ("ACPI: Add support for exposing BGRT data")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1406
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Thanks for solving this!
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
prev parent reply other threads:[~2021-06-23 16:32 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-23 1:38 [PATCH 1/2] ACPI: bgrt: Fix CFI violation Nathan Chancellor
2021-06-23 1:38 ` [PATCH 2/2] ACPI: bgrt: Use sysfs_emit Nathan Chancellor
2021-06-23 5:51 ` Kees Cook
2021-06-23 16:28 ` Nathan Chancellor
2021-06-23 16:32 ` Kees Cook
2021-06-23 17:29 ` Rafael J. Wysocki
2021-06-23 16:32 ` Kees Cook [this message]
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