Messages in this thread | | | Date | Fri, 05 Sep 2014 17:45:03 -0700 | From | Behan Webster <> | Subject | Re: [PATCH] security, crypto: LLVMLinux: Remove VLAIS from ima_crypto.c |
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On 09/05/14 17:18, Thomas Gleixner wrote: > On Fri, 5 Sep 2014, behanw@converseincode.com wrote: > >> From: Behan Webster <behanw@converseincode.com> >> >> Replaced the use of a Variable Length Array In Struct (VLAIS) with a C99 >> compliant equivalent. This patch allocates the appropriate amount of memory >> using an char array. >> >> The new code can be compiled with both gcc and clang. >> >> struct shash_desc contains a flexible array member member ctx declared with >> CRYPTO_MINALIGN_ATTR, so sizeof(struct shash_desc) aligns the beginning >> of the array declared after struct shash_desc with long long. >> >> No trailing padding is required because it is not a struct type that can >> be used in an array. >> >> The CRYPTO_MINALIGN_ATTR is required so that desc is aligned with long long >> as would be the case for a struct containing a member with >> CRYPTO_MINALIGN_ATTR. >> >> Signed-off-by: Behan Webster <behanw@converseincode.com> >> Signed-off-by: Mark Charlebois <charlebm@gmail.com> >> Signed-off-by: Jan-Simon Möller <dl9pf@gmx.de> > This SOB chain is completely ass backwards. See Documentation/... "The Signed-off-by: tag indicates that the signer was involved in the development of the patch, or that he/she was in the patch's delivery path."
All three of us were involved. Does that not satisfy this rule?
>> --- >> security/integrity/ima/ima_crypto.c | 53 +++++++++++++++++-------------------- >> 1 file changed, 25 insertions(+), 28 deletions(-) >> >> diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c >> index 0bd7328..a6aa2b0 100644 >> --- a/security/integrity/ima/ima_crypto.c >> +++ b/security/integrity/ima/ima_crypto.c >> @@ -380,17 +380,16 @@ static int ima_calc_file_hash_tfm(struct file *file, >> loff_t i_size, offset = 0; >> char *rbuf; >> int rc, read = 0; >> - struct { >> - struct shash_desc shash; >> - char ctx[crypto_shash_descsize(tfm)]; >> - } desc; >> + char desc[sizeof(struct shash_desc) + >> + crypto_shash_descsize(tfm)] CRYPTO_MINALIGN_ATTR; >> + struct shash_desc *shash = (struct shash_desc *)desc; > That anon struct should have never happened in the first place. Sadly this is a design pattern used in many places through out the kernel, and appears to be fundamental to the crypto system. I was advised *not* to change it, so we haven't.
I agree that it's not a good practice.
> Not > your problem, but you are not making it any better. You replace open > coded crap with even more unreadable crap. > > Whats wrong with > > SHASH_DESC_ON_STACK(shash, tfm); Nothing is wrong with that. I would have actually preferred that. But it would have fundamentally changed a lot more code.
I'm not sure making fundamental changes to the crypto code in order to make "my favourite compiler happy" is really a better plan. I prefer smaller more measured steps.
> or something along that line and hide all the stack allocation, type > conversion crap and make my favourite compiler happy in a single > place? At this point it is less about making a particular compiler happy, and more about making the code at least C99 compliant which enables a different compiler so that more people can use it to make more fundamental changes like you are suggesting.
I appreciate your feedback,
Behan
-- Behan Webster behanw@converseincode.com
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