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Subject: Re: [PATCH 4.4.y] crypto: algif_skcipher - use ZERO_OR_NULL_PTR in
 skcipher_recvmsg_async
To:     <gregkh@linuxfoundation.org>, <herbert@gondor.apana.org.au>
CC:     <stable@vger.kernel.org>, <linux-crypto@vger.kernel.org>,
        <yangerkun@huawei.com>
References: <20200305085040.21551-1-yangerkun@huawei.com>
From:   yangerkun <yangerkun@huawei.com>
Message-ID: <9f3c49d6-9a12-7cec-feea-0e7b88d981b3@huawei.com>
Date:   Thu, 5 Mar 2020 16:25:54 +0800
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Drop this, the attach call trace is wrong...

I am so sorry for this. Will send v2.

On 2020/3/5 16:50, yangerkun wrote:
> Nowdays, we trigger a oops:
> ...
> kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000
> ...
>   [<ffffffff8114ab47>] do_async_page_fault+0x37/0xb0 x86/../arch/x86/kernel/kvm.c:266
>   [<ffffffff828b4a48>] async_page_fault+0x28/0x30 x86/../arch/x86/entry/entry_64.S:1043
>   [<ffffffff81b47c2a>] iov_iter_zero+0x15a/0x850 x86/../lib/iov_iter.c:445
>   [<ffffffff81e8ca2f>] read_iter_zero+0xcf/0x1b0 x86/../drivers/char/mem.c:708
>   [<ffffffff816ea7c8>] do_iter_readv_writev x86/../fs/read_write.c:679 [inline]
>   [<ffffffff816ea7c8>] do_readv_writev+0x448/0x8e0 x86/../fs/read_write.c:823
>   [<ffffffff816eacdf>] vfs_readv+0x7f/0xb0 x86/../fs/read_write.c:849
>   [<ffffffff816edac3>] SYSC_preadv x86/../fs/read_write.c:927 [inline]
>   [<ffffffff816edac3>] SyS_preadv+0x193/0x240 x86/../fs/read_write.c:913
>   [<ffffffff828b3261>] entry_SYSCALL_64_fastpath+0x1e/0x9a
>
> In skcipher_recvmsg_async, we use '!sreq->tsg' to determine does we
> calloc fail. However, kcalloc may return ZERO_SIZE_PTR, and with this,
> the latter sg_init_table will trigger the bug. Fix it be use ZERO_OF_NULL_PTR.
>
> This function was introduced with ' commit a596999b7ddf ("crypto:
> algif - change algif_skcipher to be asynchronous")', and has been removed
> with 'commit e870456d8e7c ("crypto: algif_skcipher - overhaul memory
> management")'.
>
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: yangerkun <yangerkun@huawei.com>
> ---
>   crypto/algif_skcipher.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
> index d12782dc9683..9bd4691cc5c5 100644
> --- a/crypto/algif_skcipher.c
> +++ b/crypto/algif_skcipher.c
> @@ -538,7 +538,7 @@ static int skcipher_recvmsg_async(struct socket *sock, struct msghdr *msg,
>   	lock_sock(sk);
>   	tx_nents = skcipher_all_sg_nents(ctx);
>   	sreq->tsg = kcalloc(tx_nents, sizeof(*sg), GFP_KERNEL);
> -	if (unlikely(!sreq->tsg))
> +	if (unlikely(ZERO_OR_NULL_PTR(sreq->tsg)))
>   		goto unlock;
>   	sg_init_table(sreq->tsg, tx_nents);
>   	memcpy(iv, ctx->iv, ivsize);