[PATCH 1/1] crypto: acomp: Use shared struct for context alloc and free ops

[Dan Moulding <dan@xxxxxxxx>]

In commit 42d9f6c77479 ("crypto: acomp - Move scomp stream allocation
code into acomp"), the crypto_acomp_streams struct was made to rely on
having the alloc_ctx and free_ctx operations defined in the same order
as the scomp_alg struct. But in that same commit, the alloc_ctx and
free_ctx members of scomp_alg may be randomized by structure layout
randomization, since they are contained in a pure ops structure
(containing only function pointers). If the pointers within scomp_alg
are randomized, but those in crypto_acomp_streams are not, then
the order may no longer match. This fixes the problem by defining a
shared structure that both crypto_acomp_streams and scomp_alg share:
acomp_ctx_ops. This new pure ops structure may now be randomized,
while still allowing both crypto_acomp_streams and scomp_alg to have
matching layout.

Signed-off-by: Dan Moulding <dan@xxxxxxxx>
Fixes: 42d9f6c77479 ("crypto: acomp - Move scomp stream allocation code into acomp")
---
 crypto/acompress.c                  |  6 +++---
 crypto/lz4.c                        |  6 ++++--
 include/crypto/internal/acompress.h | 10 +++++++---
 include/crypto/internal/scompress.h |  5 +----
 4 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/crypto/acompress.c b/crypto/acompress.c
index be28cbfd22e3..ff910035ee42 100644
--- a/crypto/acompress.c
+++ b/crypto/acompress.c
@@ -375,7 +375,7 @@ static void acomp_stream_workfn(struct work_struct *work)
 		if (ps->ctx)
 			continue;
 
-		ctx = s->alloc_ctx();
+		ctx = s->ctx_ops.alloc_ctx();
 		if (IS_ERR(ctx))
 			break;
 
@@ -398,7 +398,7 @@ void crypto_acomp_free_streams(struct crypto_acomp_streams *s)
 		return;
 
 	cancel_work_sync(&s->stream_work);
-	free_ctx = s->free_ctx;
+	free_ctx = s->ctx_ops.free_ctx;
 
 	for_each_possible_cpu(i) {
 		struct crypto_acomp_stream *ps = per_cpu_ptr(streams, i);
@@ -427,7 +427,7 @@ int crypto_acomp_alloc_streams(struct crypto_acomp_streams *s)
 	if (!streams)
 		return -ENOMEM;
 
-	ctx = s->alloc_ctx();
+	ctx = s->ctx_ops.alloc_ctx();
 	if (IS_ERR(ctx)) {
 		free_percpu(streams);
 		return PTR_ERR(ctx);
diff --git a/crypto/lz4.c b/crypto/lz4.c
index 7a984ae5ae52..c16c0d936708 100644
--- a/crypto/lz4.c
+++ b/crypto/lz4.c
@@ -68,8 +68,10 @@ static int lz4_sdecompress(struct crypto_scomp *tfm, const u8 *src,
 }
 
 static struct scomp_alg scomp = {
-	.alloc_ctx		= lz4_alloc_ctx,
-	.free_ctx		= lz4_free_ctx,
+	.ctx_ops                = {
+		.alloc_ctx	= lz4_alloc_ctx,
+		.free_ctx       = lz4_free_ctx,
+	},
 	.compress		= lz4_scompress,
 	.decompress		= lz4_sdecompress,
 	.base			= {
diff --git a/include/crypto/internal/acompress.h b/include/crypto/internal/acompress.h
index 2d97440028ff..c84a17ac26ca 100644
--- a/include/crypto/internal/acompress.h
+++ b/include/crypto/internal/acompress.h
@@ -55,15 +55,19 @@ struct acomp_alg {
 	};
 };
 
+struct acomp_ctx_ops {
+	void *(*alloc_ctx)(void);
+	void (*free_ctx)(void *);
+};
+
 struct crypto_acomp_stream {
 	spinlock_t lock;
 	void *ctx;
 };
 
 struct crypto_acomp_streams {
-	/* These must come first because of struct scomp_alg. */
-	void *(*alloc_ctx)(void);
-	void (*free_ctx)(void *);
+	/* This must come first because of struct scomp_alg. */
+	struct acomp_ctx_ops ctx_ops;
 
 	struct crypto_acomp_stream __percpu *streams;
 	struct work_struct stream_work;
diff --git a/include/crypto/internal/scompress.h b/include/crypto/internal/scompress.h
index 533d6c16a491..1d807a15aef2 100644
--- a/include/crypto/internal/scompress.h
+++ b/include/crypto/internal/scompress.h
@@ -35,10 +35,7 @@ struct scomp_alg {
 			  void *ctx);
 
 	union {
-		struct {
-			void *(*alloc_ctx)(void);
-			void (*free_ctx)(void *ctx);
-		};
+		struct acomp_ctx_ops ctx_ops;
 		struct crypto_acomp_streams streams;
 	};
 
-- 
2.49.1