linux-kernel - [PATCH v12 08/13] net, arm64: untag user pointers in tcp_zerocopy

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Message-Id: <80e79c47dc7c5ee3572034a1d69bb724fbed2ecb.1552929301.git.andreyknvl@google.com>
Date:   Mon, 18 Mar 2019 18:17:40 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Robin Murphy <robin.murphy@....com>,
        Kees Cook <keescook@...omium.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Shuah Khan <shuah@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Dave Martin <Dave.Martin@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v12 08/13] net, arm64: untag user pointers in tcp_zerocopy_receive

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@...gle.com>
---
 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)
-- 
2.21.0.225.g810b269d1ac-goog