Pavel Skripkin <paskripkin@xxxxxxxxx> 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>
Reviewed-by: David Howells <dhowells@xxxxxxxxxx>
