[PATCH] crypto: fix uninit-value in af_alg_free_resources

[PATCH] crypto: fix uninit-value in af_alg_free_resources

[Pavel Skripkin]

Syzbot was able to trigger use of uninitialized memory in
af_alg_free_resources.

Bug is caused by missing initialization of rsgl->sgl.need_unpin before
adding to rsgl_list. Then in case of extract_iter_to_sg() failure, rsgl
is left with uninitialized need_unpin which is read during clean up

BUG: KMSAN: uninit-value in af_alg_free_sg crypto/af_alg.c:545 [inline]
BUG: KMSAN: uninit-value in af_alg_free_areq_sgls crypto/af_alg.c:778 [inline]
BUG: KMSAN: uninit-value in af_alg_free_resources+0x3d1/0xf60 crypto/af_alg.c:1117
 af_alg_free_sg crypto/af_alg.c:545 [inline]
 af_alg_free_areq_sgls crypto/af_alg.c:778 [inline]
 af_alg_free_resources+0x3d1/0xf60 crypto/af_alg.c:1117
 _skcipher_recvmsg crypto/algif_skcipher.c:144 [inline]
...

Uninit was created at:
 slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
 slab_alloc_node mm/slub.c:3470 [inline]
 __kmem_cache_alloc_node+0x536/0x8d0 mm/slub.c:3509
 __do_kmalloc_node mm/slab_common.c:984 [inline]
 __kmalloc+0x121/0x3c0 mm/slab_common.c:998
 kmalloc include/linux/slab.h:586 [inline]
 sock_kmalloc+0x128/0x1c0 net/core/sock.c:2683
 af_alg_alloc_areq+0x41/0x2a0 crypto/af_alg.c:1188
 _skcipher_recvmsg crypto/algif_skcipher.c:71 [inline]

Fixes: c1abe6f570af ("crypto: af_alg: Use extract_iter_to_sg() to create scatterlists")
Reported-and-tested-by: syzbot+cba21d50095623218389@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=cba21d50095623218389
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 crypto/af_alg.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 06b15b9f661c..4e4f2d837481 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1241,6 +1241,8 @@ int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
 				return -ENOMEM;
 		}
 
+		rsgl->sgl.need_unpin = 0;
+
 		rsgl->sgl.sgt.sgl = rsgl->sgl.sgl;
 		rsgl->sgl.sgt.nents = 0;
 		rsgl->sgl.sgt.orig_nents = 0;
-- 
2.40.1

Re: [PATCH] crypto: fix uninit-value in af_alg_free_resources

[David Howells]

Pavel Skripkin <paskripkin@gmail.com> wrote:

> Syzbot was able to trigger use of uninitialized memory in
> af_alg_free_resources.
> 
> Bug is caused by missing initialization of rsgl->sgl.need_unpin before
> adding to rsgl_list. Then in case of extract_iter_to_sg() failure, rsgl
> is left with uninitialized need_unpin which is read during clean up

Looks feasible :-).

> +		rsgl->sgl.need_unpin = 0;
> +

The blank line isn't really necessary and it's a bool, so can you use 'false'
rather than '0'?

Alternatively, it might be better to move:

		rsgl->sgl.need_unpin =
			iov_iter_extract_will_pin(&msg->msg_iter);

up instead.

David

Re: [PATCH] crypto: fix uninit-value in af_alg_free_resources

[Pavel Skripkin]

Hi David,

David Howells <dhowells@redhat.com> says:
> Pavel Skripkin <paskripkin@gmail.com> wrote:
> 
>> Syzbot was able to trigger use of uninitialized memory in
>> af_alg_free_resources.
>> 
>> Bug is caused by missing initialization of rsgl->sgl.need_unpin before
>> adding to rsgl_list. Then in case of extract_iter_to_sg() failure, rsgl
>> is left with uninitialized need_unpin which is read during clean up
> 
> Looks feasible :-).
> 
>> +		rsgl->sgl.need_unpin = 0;
>> +
> 
> The blank line isn't really necessary and it's a bool, so can you use 'false'
> rather than '0'?
> 
> Alternatively, it might be better to move:
> 
> 		rsgl->sgl.need_unpin =
> 			iov_iter_extract_will_pin(&msg->msg_iter);
> 
> up instead.
> 

Thank you for review! I've just posted v2 :)



With regards,
Pavel Skripkin

[PATCH v2] crypto: fix uninit-value in af_alg_free_resources

[Pavel Skripkin]

Syzbot was able to trigger use of uninitialized memory in
af_alg_free_resources.

Bug is caused by missing initialization of rsgl->sgl.need_unpin before
adding to rsgl_list. Then in case of extract_iter_to_sg() failure, rsgl
is left with uninitialized need_unpin which is read during clean up

BUG: KMSAN: uninit-value in af_alg_free_sg crypto/af_alg.c:545 [inline]
BUG: KMSAN: uninit-value in af_alg_free_areq_sgls crypto/af_alg.c:778 [inline]
BUG: KMSAN: uninit-value in af_alg_free_resources+0x3d1/0xf60 crypto/af_alg.c:1117
 af_alg_free_sg crypto/af_alg.c:545 [inline]
 af_alg_free_areq_sgls crypto/af_alg.c:778 [inline]
 af_alg_free_resources+0x3d1/0xf60 crypto/af_alg.c:1117
 _skcipher_recvmsg crypto/algif_skcipher.c:144 [inline]
...

Uninit was created at:
 slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
 slab_alloc_node mm/slub.c:3470 [inline]
 __kmem_cache_alloc_node+0x536/0x8d0 mm/slub.c:3509
 __do_kmalloc_node mm/slab_common.c:984 [inline]
 __kmalloc+0x121/0x3c0 mm/slab_common.c:998
 kmalloc include/linux/slab.h:586 [inline]
 sock_kmalloc+0x128/0x1c0 net/core/sock.c:2683
 af_alg_alloc_areq+0x41/0x2a0 crypto/af_alg.c:1188
 _skcipher_recvmsg crypto/algif_skcipher.c:71 [inline]

Fixes: c1abe6f570af ("crypto: af_alg: Use extract_iter_to_sg() to create scatterlists")
Reported-and-tested-by: syzbot+cba21d50095623218389@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=cba21d50095623218389
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---

Changes since v1:
	- Move sgl.need_unpin initialization upper instead of
	  pre-initializing it with false as suggested by David

---
 crypto/af_alg.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 06b15b9f661c..10efb56d8b48 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1241,6 +1241,8 @@ int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
 				return -ENOMEM;
 		}
 
+		rsgl->sgl.need_unpin =
+			iov_iter_extract_will_pin(&msg->msg_iter);
 		rsgl->sgl.sgt.sgl = rsgl->sgl.sgl;
 		rsgl->sgl.sgt.nents = 0;
 		rsgl->sgl.sgt.orig_nents = 0;
@@ -1255,8 +1257,6 @@ int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
 		}
 
 		sg_mark_end(rsgl->sgl.sgt.sgl + rsgl->sgl.sgt.nents - 1);
-		rsgl->sgl.need_unpin =
-			iov_iter_extract_will_pin(&msg->msg_iter);
 
 		/* chain the new scatterlist with previous one */
 		if (areq->last_rsgl)
-- 
2.40.1

Re: [PATCH v2] crypto: fix uninit-value in af_alg_free_resources

[Herbert Xu]

On Mon, Aug 14, 2023 at 09:03:41PM +0300, Pavel Skripkin wrote:
> Syzbot was able to trigger use of uninitialized memory in
> af_alg_free_resources.
> 
> Bug is caused by missing initialization of rsgl->sgl.need_unpin before
> adding to rsgl_list. Then in case of extract_iter_to_sg() failure, rsgl
> is left with uninitialized need_unpin which is read during clean up
> 
> BUG: KMSAN: uninit-value in af_alg_free_sg crypto/af_alg.c:545 [inline]
> BUG: KMSAN: uninit-value in af_alg_free_areq_sgls crypto/af_alg.c:778 [inline]
> BUG: KMSAN: uninit-value in af_alg_free_resources+0x3d1/0xf60 crypto/af_alg.c:1117
>  af_alg_free_sg crypto/af_alg.c:545 [inline]
>  af_alg_free_areq_sgls crypto/af_alg.c:778 [inline]
>  af_alg_free_resources+0x3d1/0xf60 crypto/af_alg.c:1117
>  _skcipher_recvmsg crypto/algif_skcipher.c:144 [inline]
> ...
> 
> Uninit was created at:
>  slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
>  slab_alloc_node mm/slub.c:3470 [inline]
>  __kmem_cache_alloc_node+0x536/0x8d0 mm/slub.c:3509
>  __do_kmalloc_node mm/slab_common.c:984 [inline]
>  __kmalloc+0x121/0x3c0 mm/slab_common.c:998
>  kmalloc include/linux/slab.h:586 [inline]
>  sock_kmalloc+0x128/0x1c0 net/core/sock.c:2683
>  af_alg_alloc_areq+0x41/0x2a0 crypto/af_alg.c:1188
>  _skcipher_recvmsg crypto/algif_skcipher.c:71 [inline]
> 
> Fixes: c1abe6f570af ("crypto: af_alg: Use extract_iter_to_sg() to create scatterlists")
> Reported-and-tested-by: syzbot+cba21d50095623218389@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=cba21d50095623218389
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> ---
> 
> Changes since v1:
> 	- Move sgl.need_unpin initialization upper instead of
> 	  pre-initializing it with false as suggested by David
> 
> ---
>  crypto/af_alg.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH v2] crypto: fix uninit-value in af_alg_free_resources

[David Howells]

Pavel Skripkin <paskripkin@gmail.com> wrote:

> Syzbot was able to trigger use of uninitialized memory in
> af_alg_free_resources.
> 
> Bug is caused by missing initialization of rsgl->sgl.need_unpin before
> adding to rsgl_list. Then in case of extract_iter_to_sg() failure, rsgl
> is left with uninitialized need_unpin which is read during clean up
> 
> BUG: KMSAN: uninit-value in af_alg_free_sg crypto/af_alg.c:545 [inline]
> BUG: KMSAN: uninit-value in af_alg_free_areq_sgls crypto/af_alg.c:778 [inline]
> BUG: KMSAN: uninit-value in af_alg_free_resources+0x3d1/0xf60 crypto/af_alg.c:1117
>  af_alg_free_sg crypto/af_alg.c:545 [inline]
>  af_alg_free_areq_sgls crypto/af_alg.c:778 [inline]
>  af_alg_free_resources+0x3d1/0xf60 crypto/af_alg.c:1117
>  _skcipher_recvmsg crypto/algif_skcipher.c:144 [inline]
> ...
> 
> Uninit was created at:
>  slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
>  slab_alloc_node mm/slub.c:3470 [inline]
>  __kmem_cache_alloc_node+0x536/0x8d0 mm/slub.c:3509
>  __do_kmalloc_node mm/slab_common.c:984 [inline]
>  __kmalloc+0x121/0x3c0 mm/slab_common.c:998
>  kmalloc include/linux/slab.h:586 [inline]
>  sock_kmalloc+0x128/0x1c0 net/core/sock.c:2683
>  af_alg_alloc_areq+0x41/0x2a0 crypto/af_alg.c:1188
>  _skcipher_recvmsg crypto/algif_skcipher.c:71 [inline]
> 
> Fixes: c1abe6f570af ("crypto: af_alg: Use extract_iter_to_sg() to create scatterlists")
> Reported-and-tested-by: syzbot+cba21d50095623218389@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=cba21d50095623218389
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>

Reviewed-by: David Howells <dhowells@redhat.com>