Re: [PATCH v12 08/13] net, arm64: untag user pointers in tcp_zerocopy_receive
From: Eric Dumazet <edumazet@google.com>
Date: 2019-03-18 17:35:31
Also in:
bpf, linux-arch, linux-arm-kernel, linux-doc, linux-kselftest, linux-mm, lkml
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
On Mon, Mar 18, 2019 at 10:18 AM Andrey Konovalov [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- net/ipv4/tcp.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 6baa6dc1b13b..e76beb5ff1ff 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c@@ -1749,7 +1749,7 @@ EXPORT_SYMBOL(tcp_mmap); static int tcp_zerocopy_receive(struct sock *sk, struct tcp_zerocopy_receive *zc) { - unsigned long address = (unsigned long)zc->address; + unsigned long address; const skb_frag_t *frags = NULL; u32 length = 0, seq, offset; struct vm_area_struct *vma;@@ -1758,7 +1758,12 @@ static int tcp_zerocopy_receive(struct sock *sk, int inq; int ret; - if (address & (PAGE_SIZE - 1) || address != zc->address) + address = (unsigned long)untagged_addr(zc->address); + + /* The second test in this if detects if the u64->unsigned long + * conversion had any truncated bits. + */ + if (address & (PAGE_SIZE - 1) || address != untagged_addr(zc->address)) return -EINVAL; if (sk->sk_state == TCP_LISTEN)
This is quite ugly, the comment does not really help nor belong to this patch. What about using untagged_addr() only once ?
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 6baa6dc1b13b0b94b1da238668b93e167cf444fe..855a1f68c1ea9b0d07a92bd7f5e7c24840a99d3d100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c@@ -1761,6 +1761,8 @@ static int tcp_zerocopy_receive(struct sock *sk, if (address & (PAGE_SIZE - 1) || address != zc->address) return -EINVAL; + address = untagged_addr(address); + if (sk->sk_state == TCP_LISTEN) return -ENOTCONN;