[PATCH 4/4] crypto: caam - fix use-after-free KASAN issue for RSA algorithms

[Iuliana Prodan]

Here's the KASAN report:
BUG: KASAN: use-after-free in rsa_pub_done+0x70/0xe8
Read of size 1 at addr ffff00002267b614 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc1-00165-ga85dda9-dirty #21
Hardware name: LS1046A RDB Board (DT)
Call trace:
 dump_backtrace+0x0/0x260
 show_stack+0x14/0x20
 dump_stack+0xe8/0x144
 print_address_description.isra.11+0x64/0x348
 __kasan_report+0x11c/0x230
 kasan_report+0xc/0x18
 __asan_load1+0x5c/0x68
 rsa_pub_done+0x70/0xe8
 caam_jr_dequeue+0x390/0x608
 tasklet_action_common.isra.13+0x1ec/0x230
...

Fixes: bf53795025a2 ("crypto: caam - add crypto_engine support for RSA algorithms")
Signed-off-by: Iuliana Prodan <iuliana.prodan@xxxxxxx>
---
 drivers/crypto/caam/caampkc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/caam/caampkc.c b/drivers/crypto/caam/caampkc.c
index 4fcae37..59cc7116 100644
--- a/drivers/crypto/caam/caampkc.c
+++ b/drivers/crypto/caam/caampkc.c
@@ -129,7 +129,6 @@ static void rsa_pub_done(struct device *dev, u32 *desc, u32 err, void *context)
 
 	rsa_pub_unmap(dev, edesc, req);
 	rsa_io_unmap(dev, edesc, req);
-	kfree(edesc);
 
 	/*
 	 * If no backlog flag, the completion of the request is done
@@ -139,6 +138,8 @@ static void rsa_pub_done(struct device *dev, u32 *desc, u32 err, void *context)
 		akcipher_request_complete(req, ecode);
 	else
 		crypto_finalize_akcipher_request(jrp->engine, req, ecode);
+
+	kfree(edesc);
 }
 
 static void rsa_priv_f_done(struct device *dev, u32 *desc, u32 err,
@@ -170,7 +171,6 @@ static void rsa_priv_f_done(struct device *dev, u32 *desc, u32 err,
 	}
 
 	rsa_io_unmap(dev, edesc, req);
-	kfree(edesc);
 
 	/*
 	 * If no backlog flag, the completion of the request is done
@@ -180,6 +180,8 @@ static void rsa_priv_f_done(struct device *dev, u32 *desc, u32 err,
 		akcipher_request_complete(req, ecode);
 	else
 		crypto_finalize_akcipher_request(jrp->engine, req, ecode);
+
+	kfree(edesc);
 }
 
 /**
-- 
2.1.0