linux-kernel - Re: [PATCH] tpm: Do not dereference NULL pointer if acpi_os_map

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Date:	Thu, 16 Aug 2012 10:45:07 -0500
From:	Kent Yoder <key@...ux.vnet.ibm.com>
To:	Jesper Juhl <jj@...osbits.net>
Cc:	linux-kernel@...r.kernel.org, tpmdd-devel@...ts.sourceforge.net,
	Sirrix AG <tpmdd@...rix.com>,
	Marcel Selhorst <tpmdd@...horst.net>,
	Rajiv Andrade <mail@...jiv.net>,
	Seiji Munetoh <munetoh@...ibm.com>,
	Stefan Berger <stefanb@...ibm.com>,
	Reiner Sailer <sailer@...son.ibm.com>,
	Kylene Hall <kjhall@...ibm.com>
Subject: Re: [PATCH] tpm: Do not dereference NULL pointer if
 acpi_os_map_memory() fails.

On Thu, Aug 16, 2012 at 12:16:33AM +0200, Jesper Juhl wrote:
> In drivers/char/tpm/tpm_acpi.c::read_log() we call
> acpi_os_map_memory(). That call may fail for a number of reasons
> (invalid address, out of memory etc). If the call fails it returns
> NULL and we just pass that to memcpy() unconditionally, which will go
> bad when it tries to dereference the pointer.
> 
> Unfortunately we just get NULL back, so we can't really tell the user
> exactely what went wrong, but we can at least avoid crashing and
> return an error (-EIO seemed more generic and more suitable here than
> -ENOMEM or something else, so I picked that).

  Thanks Jesper, applied here:

git://github.com/shpedoikal/linux.git v3.6-rc1-tpmdd-staging

Kent

> 
> Signed-off-by: Jesper Juhl <jj@...osbits.net>
> ---
>  drivers/char/tpm/tpm_acpi.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
>  note: this patch is against git://github.com/shpedoikal/linux.git v3.6-rc1-tpmdd-staging
> 
> diff --git a/drivers/char/tpm/tpm_acpi.c b/drivers/char/tpm/tpm_acpi.c
> index a1bb5a18..fe3fa94 100644
> --- a/drivers/char/tpm/tpm_acpi.c
> +++ b/drivers/char/tpm/tpm_acpi.c
> @@ -96,6 +96,11 @@ int read_log(struct tpm_bios_log *log)
>  	log->bios_event_log_end = log->bios_event_log + len;
> 
>  	virt = acpi_os_map_memory(start, len);
> +	if (!virt) {
> +		kfree(log->bios_event_log);
> +		printk("%s: ERROR - Unable to map memory\n", __func__);
> +		return -EIO;
> +	}
> 
>  	memcpy(log->bios_event_log, virt, len);
> 
> -- 
> 1.7.11.4
> 
> 
> -- 
> Jesper Juhl <jj@...osbits.net>       http://www.chaosbits.net/
> Don't top-post http://www.catb.org/jargon/html/T/top-post.html
> Plain text mails only, please.
> 

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