[PATCH] qemu_fw_cfg: Make fw_cfg_rev_attr a proper kobj_attribute

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Nathan Chancellor

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Feb 11, 2021, 2:43:13 PM2/11/21
to Gabriel Somlo, Michael S. Tsirkin, Nick Desaulniers, Sami Tolvanen, Kees Cook, qemu-...@nongnu.org, linux-...@vger.kernel.org, clang-bu...@googlegroups.com, Nathan Chancellor
fw_cfg_showrev() is called by an indirect call in kobj_attr_show(),
which violates clang's CFI checking because fw_cfg_showrev()'s second
parameter is 'struct attribute', whereas the ->show() member of 'struct
kobj_structure' expects the second parameter to be of type 'struct
kobj_attribute'.

$ cat /sys/firmware/qemu_fw_cfg/rev
3

$ dmesg | grep "CFI failure"
[ 26.016832] CFI failure (target: fw_cfg_showrev+0x0/0x8):

Fix this by converting fw_cfg_rev_attr to 'struct kobj_attribute' where
this would have been caught automatically by the incompatible pointer
types compiler warning. Update fw_cfg_showrev() accordingly.

Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg device")
Link: https://github.com/ClangBuiltLinux/linux/issues/1299
Signed-off-by: Nathan Chancellor <nat...@kernel.org>
---
drivers/firmware/qemu_fw_cfg.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 0078260fbabe..172c751a4f6c 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -299,15 +299,13 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev)
return 0;
}

-static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char *buf)
+static ssize_t fw_cfg_showrev(struct kobject *k, struct kobj_attribute *a,
+ char *buf)
{
return sprintf(buf, "%u\n", fw_cfg_rev);
}

-static const struct {
- struct attribute attr;
- ssize_t (*show)(struct kobject *k, struct attribute *a, char *buf);
-} fw_cfg_rev_attr = {
+static const struct kobj_attribute fw_cfg_rev_attr = {
.attr = { .name = "rev", .mode = S_IRUSR },
.show = fw_cfg_showrev,
};

base-commit: 92bf22614b21a2706f4993b278017e437f7785b3
--
2.30.1

Sami Tolvanen

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Feb 11, 2021, 3:41:26 PM2/11/21
to Nathan Chancellor, Gabriel Somlo, Michael S. Tsirkin, Nick Desaulniers, Kees Cook, qemu-...@nongnu.org, LKML, clang-built-linux
Hi Nathan,

On Thu, Feb 11, 2021 at 11:43 AM Nathan Chancellor <nat...@kernel.org> wrote:
>
> fw_cfg_showrev() is called by an indirect call in kobj_attr_show(),
> which violates clang's CFI checking because fw_cfg_showrev()'s second
> parameter is 'struct attribute', whereas the ->show() member of 'struct
> kobj_structure' expects the second parameter to be of type 'struct
> kobj_attribute'.
>
> $ cat /sys/firmware/qemu_fw_cfg/rev
> 3
>
> $ dmesg | grep "CFI failure"
> [ 26.016832] CFI failure (target: fw_cfg_showrev+0x0/0x8):
>
> Fix this by converting fw_cfg_rev_attr to 'struct kobj_attribute' where
> this would have been caught automatically by the incompatible pointer
> types compiler warning. Update fw_cfg_showrev() accordingly.
>
> Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg device")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1299
> Signed-off-by: Nathan Chancellor <nat...@kernel.org>

Looks good to me. Thank you for sending the patch!

Reviewed-by: Sami Tolvanen <samito...@google.com>

Sami

Nick Desaulniers

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Feb 22, 2021, 2:02:47 PM2/22/21
to Gabriel Somlo, Michael S. Tsirkin, Sami Tolvanen, Kees Cook, qemu-...@nongnu.org, LKML, clang-built-linux, Nathan Chancellor
Did this happen to get picked up already? EOM

On Thu, Feb 11, 2021 at 11:43 AM Nathan Chancellor <nat...@kernel.org> wrote:
>
> --
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> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-li...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20210211194258.4137998-1-nathan%40kernel.org.



--
Thanks,
~Nick Desaulniers

Nathan Chancellor

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Feb 22, 2021, 2:08:09 PM2/22/21
to Nick Desaulniers, Gabriel Somlo, Michael S. Tsirkin, Sami Tolvanen, Kees Cook, qemu-...@nongnu.org, LKML, clang-built-linux
On Mon, Feb 22, 2021 at 11:02:34AM -0800, Nick Desaulniers wrote:
> Did this happen to get picked up already? EOM

I have not gotten an email saying it has been picked up nor does it
appear to be in -next.

Cheers,
Nathan

Sedat Dilek

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Feb 24, 2021, 1:09:11 PM2/24/21
to Sami Tolvanen, Nathan Chancellor, Gabriel Somlo, Michael S. Tsirkin, Nick Desaulniers, Kees Cook, qemu-...@nongnu.org, LKML, clang-built-linux
Environment: Linux v5.11-10201-gc03c21ba6f4e plus Clang-CFI as of
24-Feb-2021 on top built with LLVM v13-git.

Tested-by: Sedat Dilek <sedat...@gmail.com>

- Sedat -

Kees Cook

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Feb 24, 2021, 11:57:37 PM2/24/21
to Nathan Chancellor, Michael S. Tsirkin, Gabriel Somlo, Nick Desaulniers, Sami Tolvanen, qemu-...@nongnu.org, linux-...@vger.kernel.org, clang-bu...@googlegroups.com
On Thu, Feb 11, 2021 at 12:42:58PM -0700, Nathan Chancellor wrote:
> fw_cfg_showrev() is called by an indirect call in kobj_attr_show(),
> which violates clang's CFI checking because fw_cfg_showrev()'s second
> parameter is 'struct attribute', whereas the ->show() member of 'struct
> kobj_structure' expects the second parameter to be of type 'struct
> kobj_attribute'.
>
> $ cat /sys/firmware/qemu_fw_cfg/rev
> 3
>
> $ dmesg | grep "CFI failure"
> [ 26.016832] CFI failure (target: fw_cfg_showrev+0x0/0x8):
>
> Fix this by converting fw_cfg_rev_attr to 'struct kobj_attribute' where
> this would have been caught automatically by the incompatible pointer
> types compiler warning. Update fw_cfg_showrev() accordingly.
>
> Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg device")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1299
> Signed-off-by: Nathan Chancellor <nat...@kernel.org>

Ah, nice, yes.

Reviewed-by: Kees Cook <kees...@chromium.org>

Michael, are you able to take this? I can snag it if needed.

-Kees

> ---
> drivers/firmware/qemu_fw_cfg.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
> index 0078260fbabe..172c751a4f6c 100644
> --- a/drivers/firmware/qemu_fw_cfg.c
> +++ b/drivers/firmware/qemu_fw_cfg.c
> @@ -299,15 +299,13 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev)
> return 0;
> }
>
> -static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char *buf)
> +static ssize_t fw_cfg_showrev(struct kobject *k, struct kobj_attribute *a,
> + char *buf)
> {
> return sprintf(buf, "%u\n", fw_cfg_rev);
> }
>
> -static const struct {
> - struct attribute attr;
> - ssize_t (*show)(struct kobject *k, struct attribute *a, char *buf);
> -} fw_cfg_rev_attr = {
> +static const struct kobj_attribute fw_cfg_rev_attr = {
> .attr = { .name = "rev", .mode = S_IRUSR },
> .show = fw_cfg_showrev,
> };
>
> base-commit: 92bf22614b21a2706f4993b278017e437f7785b3
> --
> 2.30.1
>

--
Kees Cook

Philippe Mathieu-Daudé

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Feb 25, 2021, 5:42:08 AM2/25/21
to Nathan Chancellor, Gabriel Somlo, Michael S. Tsirkin, Kees Cook, Nick Desaulniers, linux-...@vger.kernel.org, qemu-...@nongnu.org, clang-bu...@googlegroups.com, Sami Tolvanen
On 2/11/21 8:42 PM, Nathan Chancellor wrote:
> fw_cfg_showrev() is called by an indirect call in kobj_attr_show(),
> which violates clang's CFI checking because fw_cfg_showrev()'s second
> parameter is 'struct attribute', whereas the ->show() member of 'struct
> kobj_structure' expects the second parameter to be of type 'struct
> kobj_attribute'.
>
> $ cat /sys/firmware/qemu_fw_cfg/rev
> 3
>
> $ dmesg | grep "CFI failure"
> [ 26.016832] CFI failure (target: fw_cfg_showrev+0x0/0x8):
>
> Fix this by converting fw_cfg_rev_attr to 'struct kobj_attribute' where
> this would have been caught automatically by the incompatible pointer
> types compiler warning. Update fw_cfg_showrev() accordingly.
>
> Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg device")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1299
> Signed-off-by: Nathan Chancellor <nat...@kernel.org>
> ---
> drivers/firmware/qemu_fw_cfg.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>

Kees Cook

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Feb 25, 2021, 4:25:17 PM2/25/21
to Gabriel Somlo, Nathan Chancellor, Michael S. Tsirkin, Kees Cook, linux-...@vger.kernel.org, Nick Desaulniers, qemu-...@nongnu.org, clang-bu...@googlegroups.com, Sami Tolvanen
On Thu, 11 Feb 2021 12:42:58 -0700, Nathan Chancellor wrote:
> fw_cfg_showrev() is called by an indirect call in kobj_attr_show(),
> which violates clang's CFI checking because fw_cfg_showrev()'s second
> parameter is 'struct attribute', whereas the ->show() member of 'struct
> kobj_structure' expects the second parameter to be of type 'struct
> kobj_attribute'.
>
> $ cat /sys/firmware/qemu_fw_cfg/rev
> 3
>
> [...]

Applied to kspp/cfi/cleanups, thanks!

[1/1] qemu_fw_cfg: Make fw_cfg_rev_attr a proper kobj_attribute
https://git.kernel.org/kees/c/f5c4679d6c49

--
Kees Cook

Sedat Dilek

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Apr 2, 2021, 2:42:45 AM4/2/21
to Kees Cook, Gabriel Somlo, Nathan Chancellor, Michael S. Tsirkin, linux-...@vger.kernel.org, Nick Desaulniers, qemu-...@nongnu.org, Clang-Built-Linux ML, Sami Tolvanen
I have queued this up in my custom patchset
(for-5.12/kspp-cfi-cleanups-20210225).

What is the plan to get this upstream?

Feel free to add my:

Kees Cook

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Apr 2, 2021, 2:25:45 PM4/2/21
to Sedat Dilek, Gabriel Somlo, Nathan Chancellor, Michael S. Tsirkin, linux-...@vger.kernel.org, Nick Desaulniers, qemu-...@nongnu.org, Clang-Built-Linux ML, Sami Tolvanen
I haven't sent it to Linus yet -- I was expecting to batch more of these
and send them for v5.13. (But if the kvm folks snag it, that's good
too.)

-Kees

>
> Feel free to add my:
>
> Tested-by: Sedat Dilek <sedat...@gmail.com>
>
> - Sedat -

--
Kees Cook

Nathan Chancellor

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Apr 2, 2021, 2:31:17 PM4/2/21
to Kees Cook, Sedat Dilek, Gabriel Somlo, Michael S. Tsirkin, linux-...@vger.kernel.org, Nick Desaulniers, qemu-...@nongnu.org, Clang-Built-Linux ML, Sami Tolvanen
I am going to be putting the CFI series through its paces on both arm64
and x86_64 over the next week or so on several different machines (in
fact, I am writing up a report right now) so I will probably have some
more of these as I find them.

Cheers,
Nathan

Sedat Dilek

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Apr 2, 2021, 2:45:26 PM4/2/21
to Nathan Chancellor, Kees Cook, Gabriel Somlo, Michael S. Tsirkin, linux-...@vger.kernel.org, Nick Desaulniers, qemu-...@nongnu.org, Clang-Built-Linux ML, Sami Tolvanen
This was just a friendly ping.

Sami has sent some patches which I reported in the early stage of
clang-cfi (x86-64) through subtree maintainers.
It's up to you Nathan or kvm folks.

Upstreamed patches means to me a RDC-ed custom patchset.

- Sedat -
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