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@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=cba21d50095623218389
> Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
> ---
> 
> 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@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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