[PATCH] crypto: essiv: fix use-after-free in AEAD path

[Jérémy Jean]

The request that ESSIV submits to its wrapped AEAD transform may
finish before crypto_aead_encrypt() or crypto_aead_decrypt() returns.
In case this happens, essiv_aead_done() calls aead_request_complete()
on the original ESSIV request, which can end up freeing the request
before essiv_aead_crypt() resumes, creating a UAF:

  BUG: KASAN: slab-use-after-free in essiv_aead_crypt+0x8e6/0x950
  Read of size 8 at addr ffff888102af1360 by task init/66

Keep the temporary assoc pointer in a local variable before submitting
that request.

Fixes: be1eb7f78aa8 ("crypto: essiv - create wrapper template for ESSIV generation")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: LLM
Signed-off-by: Jérémy Jean <Jeremy.Jean@xxxxxxxxxxxxxxxxx>
---
 crypto/essiv.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crypto/essiv.c b/crypto/essiv.c
index a47a3eab6935..d85136feaf3b 100644
--- a/crypto/essiv.c
+++ b/crypto/essiv.c
@@ -189,6 +189,7 @@ static int essiv_aead_crypt(struct aead_request *req, bool enc)
 	int ivsize = crypto_aead_ivsize(tfm);
 	int ssize = req->assoclen - ivsize;
 	struct scatterlist *src = req->src;
+	u8 *assoc;
 	int err;
 
 	if (ssize < 0)
@@ -247,11 +248,12 @@ static int essiv_aead_crypt(struct aead_request *req, bool enc)
 				  essiv_aead_done, req);
 	aead_request_set_crypt(subreq, src, req->dst, req->cryptlen, req->iv);
 
+	assoc = rctx->assoc;
 	err = enc ? crypto_aead_encrypt(subreq) :
 		    crypto_aead_decrypt(subreq);
 
-	if (rctx->assoc && err != -EINPROGRESS && err != -EBUSY)
-		kfree(rctx->assoc);
+	if (assoc && err != -EINPROGRESS && err != -EBUSY)
+		kfree(assoc);
 	return err;
 }
 
-- 
2.47.3