linux-kernel - [PATCH] crypto: hash - Do not use shash in hard IRQs

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Message-ID: <Z-3zfJ5hRl3_tZxJ@gondor.apana.org.au>
Date: Thu, 3 Apr 2025 10:33:32 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Eric Biggers <ebiggers@...nel.org>
Cc: Ard Biesheuvel <ardb@...nel.org>, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	"Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] crypto: hash - Do not use shash in hard IRQs

On Thu, Apr 03, 2025 at 02:14:53AM +0000, Eric Biggers wrote:
>
> The thing I actually have more of a problem with is that you tend to start
> making random API changes without any of the necessary prerequisites like
> updating documentation, or adding debug assertions to catch violations of new
> requirements.  You've already started removing the fallbacks from shash (commit
> 3846c01d42526bc31), but neither of those things have been done.  So we're
> currently in a weird state where the shash API is explicitly documented to work
> in all contexts, but you've broken that.

The documentation is easy enough to fix.

---8<---
Update the documentation to be consistent with the fact that shash
may not be used in hard IRQs.

Reported-by: Eric Biggers <ebiggers@...nel.org>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index 58f9d3c9d006..5fde27039a06 100644
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -847,7 +847,7 @@ static inline void *shash_desc_ctx(struct shash_desc *desc)
  * cipher handle must point to a keyed message digest cipher in order for this
  * function to succeed.
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 if the setting of the key was successful; < 0 if an error occurred
  */
 int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
@@ -864,7 +864,7 @@ int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
  * crypto_shash_update and crypto_shash_final. The parameters have the same
  * meaning as discussed for those separate three functions.
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 if the message digest creation was successful; < 0 if an error
  *	   occurred
  */
@@ -884,7 +884,7 @@ int crypto_shash_digest(struct shash_desc *desc, const u8 *data,
  * directly, and it allocates a hash descriptor on the stack internally.
  * Note that this stack allocation may be fairly large.
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 on success; < 0 if an error occurred.
  */
 int crypto_shash_tfm_digest(struct crypto_shash *tfm, const u8 *data,
@@ -902,7 +902,7 @@ int crypto_hash_digest(struct crypto_ahash *tfm, const u8 *data,
  * caller-allocated output buffer out which must have sufficient size (e.g. by
  * calling crypto_shash_descsize).
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 if the export creation was successful; < 0 if an error occurred
  */
 int crypto_shash_export(struct shash_desc *desc, void *out);
@@ -916,7 +916,7 @@ int crypto_shash_export(struct shash_desc *desc, void *out);
  * the input buffer. That buffer should have been generated with the
  * crypto_ahash_export function.
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 if the import was successful; < 0 if an error occurred
  */
 int crypto_shash_import(struct shash_desc *desc, const void *in);
@@ -929,7 +929,7 @@ int crypto_shash_import(struct shash_desc *desc, const void *in);
  * operational state handle. Any potentially existing state created by
  * previous operations is discarded.
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 if the message digest initialization was successful; < 0 if an
  *	   error occurred
  */
@@ -951,7 +951,7 @@ static inline int crypto_shash_init(struct shash_desc *desc)
  *
  * Updates the message digest state of the operational state handle.
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 if the message digest update was successful; < 0 if an error
  *	   occurred
  */
@@ -968,7 +968,7 @@ int crypto_shash_update(struct shash_desc *desc, const u8 *data,
  * into the output buffer. The caller must ensure that the output buffer is
  * large enough by using crypto_shash_digestsize.
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 if the message digest creation was successful; < 0 if an error
  *	   occurred
  */
@@ -985,7 +985,7 @@ int crypto_shash_final(struct shash_desc *desc, u8 *out);
  * crypto_shash_update and crypto_shash_final. The parameters have the same
  * meaning as discussed for those separate functions.
  *
- * Context: Any context.
+ * Context: Softirq or process context.
  * Return: 0 if the message digest creation was successful; < 0 if an error
  *	   occurred
  */
-- 
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