[PATCH 3/4] crypto: caam - fix use-after-free KASAN issue for HASH algorithms

[Iuliana Prodan]

Here's the KASAN report:
BUG: KASAN: use-after-free in ahash_done+0xdc/0x3b8
Read of size 1 at addr ffff000022e75510 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc1-00164-gcb59d59-dirty #20
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
 ahash_done+0xdc/0x3b8
 caam_jr_dequeue+0x390/0x608
 tasklet_action_common.isra.13+0x1ec/0x230

Fixes: 21b014f038d3 ("crypto: caam - add crypto_engine support for HASH algorithms")
Signed-off-by: Iuliana Prodan <iuliana.prodan@xxxxxxx>
---
 drivers/crypto/caam/caamhash.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/caam/caamhash.c b/drivers/crypto/caam/caamhash.c
index 943bc02..3c63fe0 100644
--- a/drivers/crypto/caam/caamhash.c
+++ b/drivers/crypto/caam/caamhash.c
@@ -593,7 +593,6 @@ static inline void ahash_done_cpy(struct device *jrdev, u32 *desc, u32 err,
 
 	ahash_unmap_ctx(jrdev, edesc, req, digestsize, dir);
 	memcpy(req->result, state->caam_ctx, digestsize);
-	kfree(edesc);
 
 	print_hex_dump_debug("ctx@"__stringify(__LINE__)": ",
 			     DUMP_PREFIX_ADDRESS, 16, 4, state->caam_ctx,
@@ -607,6 +606,8 @@ static inline void ahash_done_cpy(struct device *jrdev, u32 *desc, u32 err,
 		req->base.complete(&req->base, ecode);
 	else
 		crypto_finalize_hash_request(jrp->engine, req, ecode);
+
+	kfree(edesc);
 }
 
 static void ahash_done(struct device *jrdev, u32 *desc, u32 err,
@@ -640,7 +641,6 @@ static inline void ahash_done_switch(struct device *jrdev, u32 *desc, u32 err,
 		ecode = caam_jr_strstatus(jrdev, err);
 
 	ahash_unmap_ctx(jrdev, edesc, req, ctx->ctx_len, dir);
-	kfree(edesc);
 
 	scatterwalk_map_and_copy(state->buf, req->src,
 				 req->nbytes - state->next_buflen,
@@ -668,6 +668,7 @@ static inline void ahash_done_switch(struct device *jrdev, u32 *desc, u32 err,
 	else
 		crypto_finalize_hash_request(jrp->engine, req, ecode);
 
+	kfree(edesc);
 }
 
 static void ahash_done_bi(struct device *jrdev, u32 *desc, u32 err,
-- 
2.1.0