linux-kernel - Re: [PATCH] pstore: fix crypto dependencies without compression

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Date:   Fri, 6 Apr 2018 09:01:31 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Tobias Regnery <tobias.regnery@...il.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pstore: fix crypto dependencies without compression

On Fri, Apr 6, 2018 at 8:38 AM, Tobias Regnery <tobias.regnery@...il.com> wrote:
> Commit 58eb5b670747 ("pstore: fix crypto dependencies") fixed up the crypto
> dependencies but missed the case when no compression is selected.
>
> With CONFIG_PSTORE=y, CONFIG_PSTORE_COMPRESS=n  and CONFIG_CRYPTO=m we see
> the following link error:
>
> fs/pstore/platform.o: In function `pstore_register':
> (.text+0x1b1): undefined reference to `crypto_has_alg'
> (.text+0x205): undefined reference to `crypto_alloc_base'
> fs/pstore/platform.o: In function `pstore_unregister':
> (.text+0x3b0): undefined reference to `crypto_destroy_tfm'
>
> Fix this by selecting CONFIG_CRYPTO unconditionally.
>
> Fixes: 58eb5b670747 ("pstore: fix crypto dependencies")
> Signed-off-by: Tobias Regnery <tobias.regnery@...il.com>

Thanks, I wonder how I missed this one. Thanks for fixing it up.
It's a bit unfortunate that it now disallows the otherwise valid
CONFIG_PSTORE=y, CONFIG_PSTORE_COMPRESS=n
and CONFIG_CRYPTO=n configuration, though.

Could we do this by making the calls compile-time configured
in the pstore code instead? Please try the untested version
below.

        Arnd

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 1143ef351c58..dc720573fd53 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -258,7 +258,7 @@ static int pstore_decompress(void *in, void *out,

 static void allocate_buf_for_compression(void)
 {
-       if (!zbackend)
+       if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
                return;

        if (!crypto_has_comp(zbackend->name, 0, 0)) {
@@ -287,7 +287,7 @@ static void allocate_buf_for_compression(void)

 static void free_buf_for_compression(void)
 {
-       if (!IS_ERR_OR_NULL(tfm))
+       if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && !IS_ERR_OR_NULL(tfm))
                crypto_free_comp(tfm);
        kfree(big_oops_buf);
        big_oops_buf = NULL;