Ping? On 06/19/2014 11:23 PM, Sasha Levin wrote: > Right now userspace can pass a large chunk of data and the kernel > will attempt to allocate all of it to copy it in from userspace. > > The problem is that there is no upper limit on the size userspace > can pass. Right now userspace can even force a machine to run out > of memory by forcing the kernel to allocate large chunks of memory. > > To avoid imposing a limit, instead of allocating the entire block, > we can allocate just the size of the biggest frag possible and read > it from userspace one frag at a time. > > Signed-off-by: Sasha Levin <[email protected]> > --- > > ** WARNING: COMPLETELY UNTESTED ** (I don't have the hardware). > > net/nfc/llcp_commands.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c > index a3ad69a..da68924 100644 > --- a/net/nfc/llcp_commands.c > +++ b/net/nfc/llcp_commands.c > @@ -727,27 +727,27 @@ int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, > u8 ssap, u8 dsap, > if (local == NULL) > return -ENODEV; > > - msg_data = kzalloc(len, GFP_KERNEL); > + remote_miu = sock->remote_miu > LLCP_MAX_MIU ? > + local->remote_miu : sock->remote_miu; > + > + msg_data = kzalloc(remote_miu, GFP_KERNEL); > if (msg_data == NULL) > return -ENOMEM; > > - if (memcpy_fromiovec(msg_data, msg->msg_iov, len)) { > - kfree(msg_data); > - return -EFAULT; > - } > - > remaining_len = len; > msg_ptr = msg_data; > > do { > - remote_miu = sock->remote_miu > LLCP_MAX_MIU ? > - local->remote_miu : sock->remote_miu; > - > frag_len = min_t(size_t, remote_miu, remaining_len); > > pr_debug("Fragment %zd bytes remaining %zd", > frag_len, remaining_len); > > + if (memcpy_fromiovec(msg_data, msg->msg_iov, frag_len)) { > + kfree(msg_data); > + return -EFAULT; > + } > + > pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT, > frag_len + LLCP_HEADER_SIZE, &err); > if (pdu == NULL) { >
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