Limit sysctl_tcp_mem and sysctl_udp_mem initializers to prevent integer overflows.

[ Upstream fixed this in a different way as parts of the commits:
	8d987e5c7510 (net: avoid limits overflow)
	a9febbb4bd13 (sysctl: min/max bounds are optional)
	27b3d80a7b6a (sysctl: fix min/max handling in __do_proc_doulongvec_minmax())
 -DaveM ]
 
On a 16TB x86_64 machine, sysctl_tcp_mem[2], sysctl_udp_mem[2], and
sysctl_sctp_mem[2] can integer overflow.  Set limit such that they are
maximized without overflowing.

Signed-off-by: Robin Holt <holt@sgi.com>
To: "David S. Miller" <davem@davemloft.net>
Cc: Willy Tarreau <w@1wt.eu>
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-sctp@vger.kernel.org
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: "Pekka Savola (ipv6)" <pekkas@netcore.fi>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Vlad Yasevich <vladislav.yasevich@hp.com>
Cc: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 9 insertions, 3 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9440ba6f72ee..06a800c18b57 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2754,12 +2754,14 @@ void __init tcp_init(void)
 
 	/* Set the pressure threshold to be a fraction of global memory that
 	 * is up to 1/2 at 256 MB, decreasing toward zero with the amount of
-	 * memory, with a floor of 128 pages.
+	 * memory, with a floor of 128 pages, and a ceiling that prevents an
+	 * integer overflow.
 	 */
 	nr_pages = totalram_pages - totalhigh_pages;
 	limit = min(nr_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
 	limit = (limit * (nr_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
 	limit = max(limit, 128UL);
+	limit = min(limit, INT_MAX * 4UL / 3 / 2);
 	sysctl_tcp_mem[0] = limit / 4 * 3;
 	sysctl_tcp_mem[1] = limit;
 	sysctl_tcp_mem[2] = sysctl_tcp_mem[0] * 2;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index a9b62ee588f0..0ef8809be319 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1722,11 +1722,13 @@ void __init udp_init(void)
 
 	/* Set the pressure threshold up by the same strategy of TCP. It is a
 	 * fraction of global memory that is up to 1/2 at 256 MB, decreasing
-	 * toward zero with the amount of memory, with a floor of 128 pages.
+	 * toward zero with the amount of memory, with a floor of 128 pages,
+	 * and a ceiling that prevents an integer overflow.
 	 */
 	limit = min(nr_all_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
 	limit = (limit * (nr_all_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
 	limit = max(limit, 128UL);
+	limit = min(limit, INT_MAX * 4UL / 3 / 2);
 	sysctl_udp_mem[0] = limit / 4 * 3;
 	sysctl_udp_mem[1] = limit;
 	sysctl_udp_mem[2] = sysctl_udp_mem[0] * 2;
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 0b65354aaf64..8ef36ca39b1e 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1179,7 +1179,8 @@ SCTP_STATIC __init int sctp_init(void)
 
 	/* Set the pressure threshold to be a fraction of global memory that
 	 * is up to 1/2 at 256 MB, decreasing toward zero with the amount of
-	 * memory, with a floor of 128 pages.
+	 * memory, with a floor of 128 pages, and a ceiling that prevents an
+	 * integer overflow.
 	 * Note this initalizes the data in sctpv6_prot too
 	 * Unabashedly stolen from tcp_init
 	 */
@@ -1187,6 +1188,7 @@ SCTP_STATIC __init int sctp_init(void)
 	limit = min(nr_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
 	limit = (limit * (nr_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
 	limit = max(limit, 128UL);
+	limit = min(limit, INT_MAX * 4UL / 3 / 2);
 	sysctl_sctp_mem[0] = limit / 4 * 3;
 	sysctl_sctp_mem[1] = limit;
 	sysctl_sctp_mem[2] = sysctl_sctp_mem[0] * 2;