Messages in this thread | | | Date | Thu, 14 Dec 2006 10:10:02 -0400 | From | Anderson Briglia <> | Subject | Re: [PATCH 2/4] Add MMC Password Protection (lock/unlock) support V8: mmc_key_retention.diff |
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Hi,
ext Frank Seidel wrote: > Quoting Anderson Briglia <anderson.briglia@indt.org.br>: >> [...] > Hi, > thats really cool stuff you're providing with your patches. :) > I have some feedback or questions some parts here. > But as i just started trying to get into kernelhacking you probably > better don't take my notes to serious, please.
All comments are welcome, thanks for the revision. :)
> >> Index: linux-linus-2.6/drivers/mmc/mmc_sysfs.c >> =================================================================== >> --- linux-linus-2.6.orig/drivers/mmc/mmc_sysfs.c 2006-12-04 [...] >> +static int mmc_key_instantiate(struct key *key, const void *data, >> size_t datalen) >> +{ >> + struct mmc_key_payload *mpayload, *zap; >> + int ret; >> + >> + zap = NULL; > What is zap here for? future use? > And wouldn't it be good to also initialize mplayload here?
The code was based on code presents at security/keys/user_defined.c. This is the reason of why the MMC PWD code was implemented using this returns types and others implementations. That file (user_defined.c) implements generic functions to handle keys inside the kernel, using the Kernel Key Retention Service. Maybe you can take a look there, :). That zap variable was used to expand the key payload when a new password exceeded a previous configured size. But the Kernel Key Retention Service has changed and that zap variable is not used on key_instantiate function implemented at user_defined.c, anymore. I'll update the MMC PWD code.
> >> + ret = -EINVAL; > Is there a special reason why you already assign the errors to the > return value variable before its clear that the assignment is needed?
See the reply above. > > >> + if (datalen <= 0 || datalen > MMC_KEYLEN_MAXBYTES || !data) { > Isn't the last "|| !data" redundant as you already tested if datalen ==0?
data = 0 is different from !data.
> >> + pr_debug("Invalid data\n"); >> + goto error; >> + } >> + >> + ret = key_payload_reserve(key, datalen); >> + if (ret < 0) { >> + pr_debug("ret = %d\n", ret); >> + goto error; >> + } >> + >> + ret = -ENOMEM; > Same as above: Why do you in any case want to assign it here?
Reply above. > >> + mpayload = kmalloc(sizeof(*mpayload) + datalen, GFP_KERNEL); > I may be totally wrong, but is dereferencing a not initialized pointer > (even just for using sizeof) really ok?
Yes. I believe sizeof is a compiler operation and it does not access the data pointed by that pointer, it access just the type of the pointer.
Wouldn't it be safer to use > a sizeof(struct mmc_key_payload) here?
I believe there is no difference on using this one and that other declaration.
Thanks,
Anderson Briglia - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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