crypto: api - Use work queue in crypto_destroy_instance

[ Upstream commit 9ae4577 ] The function crypto_drop_spawn expects to be called in process context. However, when an instance is unregistered while it still has active users, the last user may cause the instance to be freed in atomic context. Fix this by delaying the freeing to a work queue. Fixes: 6bfd480 ("[CRYPTO] api: Added spawns") Reported-by: Florent Revest <revest@chromium.org> Reported-by: syzbot+d769eed29cc42d75e2a3@syzkaller.appspotmail.com Reported-by: syzbot+610ec0671f51e838436e@syzkaller.appspotmail.com Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Tested-by: Florent Revest <revest@chromium.org> Acked-by: Florent Revest <revest@chromium.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Sasha Levin <sashal@kernel.org>
xanmod · Sep 13, 2023 · c4cb61c · c4cb61c
1 parent 501f77c
commit c4cb61c
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Showing 2 changed files with 17 additions and 2 deletions.
diff --git a/crypto/algapi.c b/crypto/algapi.c
@@ -17,6 +17,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/workqueue.h>
 
 #include "internal.h"
 
@@ -74,15 +75,26 @@ static void crypto_free_instance(struct crypto_instance *inst)
 	inst->alg.cra_type->free(inst);
 }
 
-static void crypto_destroy_instance(struct crypto_alg *alg)
+static void crypto_destroy_instance_workfn(struct work_struct *w)
 {
-	struct crypto_instance *inst = (void *)alg;
+	struct crypto_instance *inst = container_of(w, struct crypto_instance,
+						    free_work);
 	struct crypto_template *tmpl = inst->tmpl;
 
 	crypto_free_instance(inst);
 	crypto_tmpl_put(tmpl);
 }
 
+static void crypto_destroy_instance(struct crypto_alg *alg)
+{
+	struct crypto_instance *inst = container_of(alg,
+						    struct crypto_instance,
+						    alg);
+
+	INIT_WORK(&inst->free_work, crypto_destroy_instance_workfn);
+	schedule_work(&inst->free_work);
+}
+
 /*
  * This function adds a spawn to the list secondary_spawns which
  * will be used at the end of crypto_remove_spawns to unregister

diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h
@@ -12,6 +12,7 @@
 #include <linux/kconfig.h>
 #include <linux/list.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 
 #include <asm/unaligned.h>
 
@@ -60,6 +61,8 @@ struct crypto_instance {
 		struct crypto_spawn *spawns;
 	};
 
+	struct work_struct free_work;
+
 	void *__ctx[] CRYPTO_MINALIGN_ATTR;
 };