netdev - Re: [PATCH] sunrpc: Improve exception handling in krb5_etm

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Date: Mon, 1 Jan 2024 12:24:59 +0100
From: Markus Elfring <Markus.Elfring@....de>
To: Chuck Lever <chuck.lever@...cle.com>, linux-nfs@...r.kernel.org,
 netdev@...r.kernel.org, kernel-janitors@...r.kernel.org
Cc: Anna Schumaker <anna@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
 Dai Ngo <Dai.Ngo@...cle.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Herbert Xu
 <herbert@...dor.apana.org.au>, Jakub Kicinski <kuba@...nel.org>,
 Jeff Layton <jlayton@...nel.org>, Neil Brown <neilb@...e.de>,
 Olga Kornievskaia <kolga@...app.com>, Paolo Abeni <pabeni@...hat.com>,
 Simo Sorce <simo@...hat.com>, Tom Talpey <tom@...pey.com>,
 Trond Myklebust <trond.myklebust@...merspace.com>,
 LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sunrpc: Improve exception handling in krb5_etm_checksum()

…
>> Thus use another label.
…
>> ---
>>  net/sunrpc/auth_gss/gss_krb5_crypto.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
…
> As has undoubtedly been pointed out in other forums, calling kfree()
> with a NULL argument is perfectly valid.

The function call “kfree(NULL)” is not really useful for error/exception handling
while it is tolerated at various source code places.

>                                          Since this small GFP_KERNEL
> allocation almost never fails, it's unlikely this change is going to
> make any difference except for readability.

I became curious if development interests can grow for the usage of
an additional label.
https://wiki.sei.cmu.edu/confluence/display/c/MEM12-C.+Consider+using+a+goto+chain+when+leaving+a+function+on+error+when+using+and+releasing+resources

> Now if we want to clean up the error flows in here to look more
> idiomatic, how about this:
…
> +++ b/net/sunrpc/auth_gss/gss_krb5_crypto.c
…
> @@ -970,8 +970,9 @@ u32 krb5_etm_checksum(struct crypto_sync_skcipher *cipher,
>
>  out_free_ahash:
>  	ahash_request_free(req);
> -out_free_mem:
> +out_free_iv:
>  	kfree(iv);
> +out_free_cksumdata:
>  	kfree_sensitive(checksumdata);
…

I find it nice that you show another possible adjustment of corresponding identifiers.

Regards,
Markus