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From:   Ard Biesheuvel <ardb@kernel.org>
To:     linux-crypto@vger.kernel.org
Cc:     herbert@gondor.apana.org.au, Ard Biesheuvel <ardb@kernel.org>,
        syzbot+12cf5fbfdeba210a89dd@syzkaller.appspotmail.com,
        Eric Biggers <ebiggers@google.com>
Subject: [PATCH v3] crypto: api - check for ERR pointers in crypto_destroy_tfm()
Date:   Tue,  2 Mar 2021 21:33:03 +0100
Message-Id: <20210302203303.40881-1-ardb@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Given that crypto_alloc_tfm() may return ERR pointers, and to avoid
crashes on obscure error paths where such pointers are presented to
crypto_destroy_tfm() (such as [0]), add an ERR_PTR check there
before dereferencing the second argument as a struct crypto_tfm
pointer.

[0] https://lore.kernel.org/linux-crypto/000000000000de949705bc59e0f6@google.com/

Reported-by: syzbot+12cf5fbfdeba210a89dd@syzkaller.appspotmail.com
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
v3: missed crypto_free_shash() in v2
    add Eric's Rb
v2: update kerneldoc comments of callers to crypto_destroy_tfm() that NULL or
    error pointers are ignored.

 crypto/api.c               | 2 +-
 include/crypto/acompress.h | 2 ++
 include/crypto/aead.h      | 2 ++
 include/crypto/akcipher.h  | 2 ++
 include/crypto/hash.h      | 4 ++++
 include/crypto/kpp.h       | 2 ++
 include/crypto/rng.h       | 2 ++
 include/crypto/skcipher.h  | 2 ++
 8 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/crypto/api.c b/crypto/api.c
index ed08cbd5b9d3..c4eda56cff89 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -562,7 +562,7 @@ void crypto_destroy_tfm(void *mem, struct crypto_tfm *tfm)
 {
 	struct crypto_alg *alg;
 
-	if (unlikely(!mem))
+	if (IS_ERR_OR_NULL(mem))
 		return;
 
 	alg = tfm->__crt_alg;
diff --git a/include/crypto/acompress.h b/include/crypto/acompress.h
index fcde59c65a81..cb3d6b1c655d 100644
--- a/include/crypto/acompress.h
+++ b/include/crypto/acompress.h
@@ -165,6 +165,8 @@ static inline struct crypto_acomp *crypto_acomp_reqtfm(struct acomp_req *req)
  * crypto_free_acomp() -- free ACOMPRESS tfm handle
  *
  * @tfm:	ACOMPRESS tfm handle allocated with crypto_alloc_acomp()
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_acomp(struct crypto_acomp *tfm)
 {
diff --git a/include/crypto/aead.h b/include/crypto/aead.h
index fcc12c593ef8..e728469c4ccc 100644
--- a/include/crypto/aead.h
+++ b/include/crypto/aead.h
@@ -185,6 +185,8 @@ static inline struct crypto_tfm *crypto_aead_tfm(struct crypto_aead *tfm)
 /**
  * crypto_free_aead() - zeroize and free aead handle
  * @tfm: cipher handle to be freed
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_aead(struct crypto_aead *tfm)
 {
diff --git a/include/crypto/akcipher.h b/include/crypto/akcipher.h
index 1d3aa252caba..5764b46bd1ec 100644
--- a/include/crypto/akcipher.h
+++ b/include/crypto/akcipher.h
@@ -174,6 +174,8 @@ static inline struct crypto_akcipher *crypto_akcipher_reqtfm(
  * crypto_free_akcipher() - free AKCIPHER tfm handle
  *
  * @tfm: AKCIPHER tfm handle allocated with crypto_alloc_akcipher()
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_akcipher(struct crypto_akcipher *tfm)
 {
diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index 13f8a6a54ca8..b2bc1e46e86a 100644
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -281,6 +281,8 @@ static inline struct crypto_tfm *crypto_ahash_tfm(struct crypto_ahash *tfm)
 /**
  * crypto_free_ahash() - zeroize and free the ahash handle
  * @tfm: cipher handle to be freed
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_ahash(struct crypto_ahash *tfm)
 {
@@ -724,6 +726,8 @@ static inline struct crypto_tfm *crypto_shash_tfm(struct crypto_shash *tfm)
 /**
  * crypto_free_shash() - zeroize and free the message digest handle
  * @tfm: cipher handle to be freed
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_shash(struct crypto_shash *tfm)
 {
diff --git a/include/crypto/kpp.h b/include/crypto/kpp.h
index 88b591215d5c..cccceadc164b 100644
--- a/include/crypto/kpp.h
+++ b/include/crypto/kpp.h
@@ -154,6 +154,8 @@ static inline void crypto_kpp_set_flags(struct crypto_kpp *tfm, u32 flags)
  * crypto_free_kpp() - free KPP tfm handle
  *
  * @tfm: KPP tfm handle allocated with crypto_alloc_kpp()
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_kpp(struct crypto_kpp *tfm)
 {
diff --git a/include/crypto/rng.h b/include/crypto/rng.h
index 8b4b844b4eef..17bb3673d3c1 100644
--- a/include/crypto/rng.h
+++ b/include/crypto/rng.h
@@ -111,6 +111,8 @@ static inline struct rng_alg *crypto_rng_alg(struct crypto_rng *tfm)
 /**
  * crypto_free_rng() - zeroize and free RNG handle
  * @tfm: cipher handle to be freed
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_rng(struct crypto_rng *tfm)
 {
diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h
index 6a733b171a5d..ef0fc9ed4342 100644
--- a/include/crypto/skcipher.h
+++ b/include/crypto/skcipher.h
@@ -196,6 +196,8 @@ static inline struct crypto_tfm *crypto_skcipher_tfm(
 /**
  * crypto_free_skcipher() - zeroize and free cipher handle
  * @tfm: cipher handle to be freed
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_skcipher(struct crypto_skcipher *tfm)
 {
-- 
2.30.1