[PATCH] crypto: acomp - Fix CFI failure due to type punning

[Eric Biggers <ebiggers@kernel.org>]

To avoid a crash when control flow integrity is enabled, make the
workspace ("stream") free function use a consistent type, and call it
through a function pointer that has that same type.

Fixes: 42d9f6c77479 ("crypto: acomp - Move scomp stream allocation code into acomp")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 crypto/deflate.c                    | 7 ++++++-
 crypto/zstd.c                       | 7 ++++++-
 include/crypto/internal/acompress.h | 5 +----
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/crypto/deflate.c b/crypto/deflate.c
index fe8e4ad0fee10..21404515dc77e 100644
--- a/crypto/deflate.c
+++ b/crypto/deflate.c
@@ -46,13 +46,18 @@ static void *deflate_alloc_stream(void)
 	ctx->stream.workspace = ctx->workspace;
 
 	return ctx;
 }
 
+static void deflate_free_stream(void *ctx)
+{
+	kvfree(ctx);
+}
+
 static struct crypto_acomp_streams deflate_streams = {
 	.alloc_ctx = deflate_alloc_stream,
-	.cfree_ctx = kvfree,
+	.free_ctx = deflate_free_stream,
 };
 
 static int deflate_compress_one(struct acomp_req *req,
 				struct deflate_stream *ds)
 {
diff --git a/crypto/zstd.c b/crypto/zstd.c
index 657e0cf7b9524..ff5f596a4ea7e 100644
--- a/crypto/zstd.c
+++ b/crypto/zstd.c
@@ -52,13 +52,18 @@ static void *zstd_alloc_stream(void)
 	ctx->wksp_size = wksp_size;
 
 	return ctx;
 }
 
+static void zstd_free_stream(void *ctx)
+{
+	kvfree(ctx);
+}
+
 static struct crypto_acomp_streams zstd_streams = {
 	.alloc_ctx = zstd_alloc_stream,
-	.cfree_ctx = kvfree,
+	.free_ctx = zstd_free_stream,
 };
 
 static int zstd_init(struct crypto_acomp *acomp_tfm)
 {
 	int ret = 0;
diff --git a/include/crypto/internal/acompress.h b/include/crypto/internal/acompress.h
index ffffd88bbbad3..2d97440028ffd 100644
--- a/include/crypto/internal/acompress.h
+++ b/include/crypto/internal/acompress.h
@@ -61,14 +61,11 @@ struct crypto_acomp_stream {
 };
 
 struct crypto_acomp_streams {
 	/* These must come first because of struct scomp_alg. */
 	void *(*alloc_ctx)(void);
-	union {
-		void (*free_ctx)(void *);
-		void (*cfree_ctx)(const void *);
-	};
+	void (*free_ctx)(void *);
 
 	struct crypto_acomp_stream __percpu *streams;
 	struct work_struct stream_work;
 	cpumask_t stream_want;
 };

base-commit: 181698af38d3f93381229ad89c09b5bd0496661a
-- 
2.50.1