crypto: pcrypt - fix freeing pcrypt instances

pcrypt is using the old way of freeing instances, where the ->free()
method specified in the 'struct crypto_template' is passed a pointer to
the 'struct crypto_instance'.  But the crypto_instance is being
kfree()'d directly, which is incorrect because the memory was actually
allocated as an aead_instance, which contains the crypto_instance at a
nonzero offset.  Thus, the wrong pointer was being kfree()'d.

Fix it by switching to the new way to free aead_instance's where the
->free() method is specified in the aead_instance itself.

Reported-by: syzbot <syzkaller@googlegroups.com>
Fixes: 0496f56065e0 ("crypto: pcrypt - Add support for new AEAD interface")
Cc: <stable@vger.kernel.org> # v4.2+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 10 insertions, 9 deletions

diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
index ee9cfb99fe25..f8ec3d4ba4a8 100644
--- a/crypto/pcrypt.c
+++ b/crypto/pcrypt.c
@@ -254,6 +254,14 @@ static void pcrypt_aead_exit_tfm(struct crypto_aead *tfm)
         crypto_free_aead(ctx->child);
 }
 
+static void pcrypt_free(struct aead_instance *inst)
+{
+        struct pcrypt_instance_ctx *ctx = aead_instance_ctx(inst);
+
+        crypto_drop_aead(&ctx->spawn);
+        kfree(inst);
+}
+
 static int pcrypt_init_instance(struct crypto_instance *inst,
                                 struct crypto_alg *alg)
 {
@@ -319,6 +327,8 @@ static int pcrypt_create_aead(struct crypto_template *tmpl, struct rtattr **tb,
         inst->alg.encrypt = pcrypt_aead_encrypt;
         inst->alg.decrypt = pcrypt_aead_decrypt;
 
+        inst->free = pcrypt_free;
+
         err = aead_register_instance(tmpl, inst);
         if (err)
                 goto out_drop_aead;
@@ -349,14 +359,6 @@ static int pcrypt_create(struct crypto_template *tmpl, struct rtattr **tb)
         return -EINVAL;
 }
 
-static void pcrypt_free(struct crypto_instance *inst)
-{
-        struct pcrypt_instance_ctx *ctx = crypto_instance_ctx(inst);
-
-        crypto_drop_aead(&ctx->spawn);
-        kfree(inst);
-}
-
 static int pcrypt_cpumask_change_notify(struct notifier_block *self,
                                         unsigned long val, void *data)
 {
@@ -469,7 +471,6 @@ static void pcrypt_fini_padata(struct padata_pcrypt *pcrypt)
 static struct crypto_template pcrypt_tmpl = {
         .name = "pcrypt",
         .create = pcrypt_create,
-        .free = pcrypt_free,
         .module = THIS_MODULE,
 };