linux-kernel - [v2 PATCH] crypto: api - Do not load modules if called by async probing

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Date: Tue, 21 May 2024 10:53:18 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Nícolas F. R. A. Prado <nfraprado@...labora.com>
Cc: Eric Biggers <ebiggers@...nel.org>, Jarkko Sakkinen <jarkko@...nel.org>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
	linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
	regressions@...ts.linux.dev, kernel@...labora.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [v2 PATCH] crypto: api - Do not load modules if called by async
 probing

On Mon, May 20, 2024 at 11:49:56AM -0400, Nícolas F. R. A. Prado wrote:
>
> Unfortunately this patch didn't work either. The warning is still there
> unchanged.

OK perhaps we can do it by calling current_is_async ourselves.
But this is really a nasty hack because it basically defeats
the whole point of loading optional algorithm by module.

Linus/Tejun, is it time perhaps to remove the warning introduced
by commit 0fdff3ec6d87856cdcc99e69cf42143fdd6c56b4 since it's
been ten years since the warning caused a real problem?

For the Crypto API, if it is called by some random driver via the
async context, this warning stops us from loading any modules
without printing a nasty warning that isn't relevant as the Crypto
API never calls async_synchronize_full.

---8<---
Do not call request_module if this is the case or a warning will
be printed.

Reported-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
Reported-by: Eric Biggers <ebiggers@...nel.org>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
---
 crypto/api.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/crypto/api.c b/crypto/api.c
index 22556907b3bc..7c4b9f86c1ad 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -10,6 +10,7 @@
  * and Nettle, by Niels Möller.
  */
 
+#include <linux/async.h>
 #include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/jump_label.h>
@@ -280,7 +281,8 @@ static struct crypto_alg *crypto_larval_lookup(const char *name, u32 type,
 	mask &= ~(CRYPTO_ALG_LARVAL | CRYPTO_ALG_DEAD);
 
 	alg = crypto_alg_lookup(name, type, mask);
-	if (!alg && !(mask & CRYPTO_NOLOAD)) {
+	if (!alg && !(mask & CRYPTO_NOLOAD) &&
+	    (!IS_BUILTIN(CONFIG_CRYPTO) || !current_is_async())) {
 		request_module("crypto-%s", name);
 
 		if (!((type ^ CRYPTO_ALG_NEED_FALLBACK) & mask &
-- 
2.39.2

-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt