Re: [PATCH v11 08/14] net, arm64: untag user pointers in tcp_zerocopy_receive

On 03/15/2019 12:51 PM, Andrey Konovalov wrote:

This patch is a part of a series that extends arm64 kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments.

tcp_zerocopy_receive() uses provided user pointers for vma lookups, which can only by done with untagged pointers.

Untag user pointers in this function.

Signed-off-by: Andrey Konovalov andreyknvl@google.com

net/ipv4/tcp.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 6baa6dc1b13b..89db3b4fc753 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1758,6 +1758,8 @@ static int tcp_zerocopy_receive(struct sock *sk, int inq; int ret;

• address = untagged_addr(address);
• if (address & (PAGE_SIZE - 1) || address != zc->address)

The second test will fail, if the top bits are changed in address but not in zc->address

return -EINVAL;