Patch "crypto: api - Use work queue in crypto_destroy_instance" has been added to the 6.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    crypto: api - Use work queue in crypto_destroy_instance

to the 6.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     crypto-api-use-work-queue-in-crypto_destroy_instance.patch
and it can be found in the queue-6.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit ee8a8911d70b881aa9f7948019849ab33bd94fd5
Author: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date:   Thu Aug 3 17:59:28 2023 +0800

    crypto: api - Use work queue in crypto_destroy_instance
    
    [ Upstream commit 9ae4577bc077a7e32c3c7d442c95bc76865c0f17 ]
    
    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: 6bfd48096ff8 ("[CRYPTO] api: Added spawns")
    Reported-by: Florent Revest <revest@xxxxxxxxxxxx>
    Reported-by: syzbot+d769eed29cc42d75e2a3@xxxxxxxxxxxxxxxxxxxxxxxxx
    Reported-by: syzbot+610ec0671f51e838436e@xxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
    Tested-by: Florent Revest <revest@xxxxxxxxxxxx>
    Acked-by: Florent Revest <revest@xxxxxxxxxxxx>
    Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/crypto/algapi.c b/crypto/algapi.c
index 5e7cd603d489c..4fe95c4480473 100644
--- 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
index 016d5a302b84a..bd3a99b0106bf 100644
--- a/include/crypto/algapi.h
+++ b/include/crypto/algapi.h
@@ -12,6 +12,7 @@
 #include <linux/cache.h>
 #include <linux/crypto.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 
 /*
  * Maximum values for blocksize and alignmask, used to allocate
@@ -83,6 +84,8 @@ struct crypto_instance {
 		struct crypto_spawn *spawns;
 	};
 
+	struct work_struct free_work;
+
 	void *__ctx[] CRYPTO_MINALIGN_ATTR;
 };