[PATCH 4.2.y-ckt 227/273] tcp: beware of alignments in tcp_get_info()

From: Kamal Mostafa
Date: Mon Mar 07 2016 - 18:18:40 EST


4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ Upstream commit ff5d749772018602c47509bdc0093ff72acd82ec ]

With some combinations of user provided flags in netlink command,
it is possible to call tcp_get_info() with a buffer that is not 8-bytes
aligned.

It does matter on some arches, so we need to use put_unaligned() to
store the u64 fields.

Current iproute2 package does not trigger this particular issue.

Fixes: 0df48c26d841 ("tcp: add tcpi_bytes_acked to tcp_info")
Fixes: 977cb0ecf82e ("tcp: add pacing_rate information into tcp_info")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
net/ipv4/tcp.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 45534a5..a7b4cf6 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -279,6 +279,7 @@

#include <asm/uaccess.h>
#include <asm/ioctls.h>
+#include <asm/unaligned.h>
#include <net/busy_poll.h>

int sysctl_tcp_fin_timeout __read_mostly = TCP_FIN_TIMEOUT;
@@ -2634,6 +2635,7 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
const struct inet_connection_sock *icsk = inet_csk(sk);
u32 now = tcp_time_stamp;
unsigned int start;
+ u64 rate64;
u32 rate;

memset(info, 0, sizeof(*info));
@@ -2698,15 +2700,17 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
info->tcpi_total_retrans = tp->total_retrans;

rate = READ_ONCE(sk->sk_pacing_rate);
- info->tcpi_pacing_rate = rate != ~0U ? rate : ~0ULL;
+ rate64 = rate != ~0U ? rate : ~0ULL;
+ put_unaligned(rate64, &info->tcpi_pacing_rate);

rate = READ_ONCE(sk->sk_max_pacing_rate);
- info->tcpi_max_pacing_rate = rate != ~0U ? rate : ~0ULL;
+ rate64 = rate != ~0U ? rate : ~0ULL;
+ put_unaligned(rate64, &info->tcpi_max_pacing_rate);

do {
start = u64_stats_fetch_begin_irq(&tp->syncp);
- info->tcpi_bytes_acked = tp->bytes_acked;
- info->tcpi_bytes_received = tp->bytes_received;
+ put_unaligned(tp->bytes_acked, &info->tcpi_bytes_acked);
+ put_unaligned(tp->bytes_received, &info->tcpi_bytes_received);
} while (u64_stats_fetch_retry_irq(&tp->syncp, start));
info->tcpi_segs_out = tp->segs_out;
info->tcpi_segs_in = tp->segs_in;
--
2.7.0