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Date: Fri, 10 Feb 2017 14:49:10 -0800
From: Joe Perches <joe@...ches.com>
To: william.c.roberts@...el.com, linux-kernel@...r.kernel.org,
apw@...onical.com
Cc: keescook@...omium.org, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v2] checkpatch: add warning on invalid %p extensions
On Fri, 2017-02-10 at 14:43 -0800, william.c.roberts@...el.com wrote:
> From: William Roberts <william.c.roberts@...el.com>
>
> The kernel supports %p extensions as documented in
> Documentation/printk-formats.txt. Warn on possibly
> improper use of non-extension characters.
>
> One issue would be the usage of %pk when %pK should have
> been used. This has a side-effect of appearing to work
> alright, but does not respect the kptr_restrict setting
> as %pK does.
>
> Sample output:
> WARNING: Invalid vsprintf pointer extension '%pk'
> + printk(KERN_INFO "Could not allocate IRQ %d for PCI Applicom device. %pk\n", dev->irq, pci_get_class); // NOT OK
>
> WARNING: Invalid vsprintf pointer extension '%pn'
> + sprintf(buf, "%pn", x); // NOT OK
>
> Signed-off-by: William Roberts <william.c.roberts@...el.com>
> ---
> scripts/checkpatch.pl | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 982c52c..fa22751 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6096,6 +6096,12 @@ sub process {
> "recursive locking is bad, do not use this ever.\n" . $herecurr);
> }
>
> +# check for vsprintf extension %p<foo> misuses
> + if (get_quoted_string($line, $rawline) =~ /(\%[\*\d\.]*p(?![\WFfSsBKRraEhMmIiUDdgVCbGN]).)/) {
> + WARN("VSPRINTF_POINTER_EXTENSION",
> + "Invalid vsprintf pointer extension '$1'\n" . $herecurr);
> + }
> +
nack.
You can't just use get_quoted_string.
You have to verify that the thing being scanned is
actually a format. There are many quoted uses of
%p like %%pil and %%pstate used by inline assembly.
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