time: jiffies_delta_to_clock_t() helper to the rescue

Various /proc/net files sometimes report crazy timer values, expressed
in clock_t units.

This happens when an expired timer delta (expires - jiffies) is passed
to jiffies_to_clock_t().

This function has an overflow in :

return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);

commit cbbc719fccdb8cb (time: Change jiffies_to_clock_t() argument type
to unsigned long) only got around the problem.

As we cant output negative values in /proc/net/tcp without breaking
various tools, I suggest adding a jiffies_delta_to_clock_t() wrapper
that caps the negative delta to a 0 value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Maciej Żenczykowski <maze@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: hank <pyu@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 8 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 42b2a6a73092..c660d2c19a2b 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2385,7 +2385,7 @@ static void get_openreq4(const struct sock *sk, const struct request_sock *req,
 			 struct seq_file *f, int i, int uid, int *len)
 {
 	const struct inet_request_sock *ireq = inet_rsk(req);
-	int ttd = req->expires - jiffies;
+	long delta = req->expires - jiffies;
 
 	seq_printf(f, "%4d: %08X:%04X %08X:%04X"
 		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %u %d %pK%n",
@@ -2397,7 +2397,7 @@ static void get_openreq4(const struct sock *sk, const struct request_sock *req,
 		TCP_SYN_RECV,
 		0, 0, /* could print option size, but that is af dependent. */
 		1,    /* timers active (only the expire timer) */
-		jiffies_to_clock_t(ttd),
+		jiffies_delta_to_clock_t(delta),
 		req->retrans,
 		uid,
 		0,  /* non standard timer */
@@ -2448,7 +2448,7 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i, int *len)
 		tp->write_seq - tp->snd_una,
 		rx_queue,
 		timer_active,
-		jiffies_to_clock_t(timer_expires - jiffies),
+		jiffies_delta_to_clock_t(timer_expires - jiffies),
 		icsk->icsk_retransmits,
 		sock_i_uid(sk),
 		icsk->icsk_probes_out,
@@ -2467,10 +2467,7 @@ static void get_timewait4_sock(const struct inet_timewait_sock *tw,
 {
 	__be32 dest, src;
 	__u16 destp, srcp;
-	int ttd = tw->tw_ttd - jiffies;
-
-	if (ttd < 0)
-		ttd = 0;
+	long delta = tw->tw_ttd - jiffies;
 
 	dest  = tw->tw_daddr;
 	src   = tw->tw_rcv_saddr;
@@ -2480,7 +2477,7 @@ static void get_timewait4_sock(const struct inet_timewait_sock *tw,
 	seq_printf(f, "%4d: %08X:%04X %08X:%04X"
 		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %pK%n",
 		i, src, srcp, dest, destp, tw->tw_substate, 0, 0,
-		3, jiffies_to_clock_t(ttd), 0, 0, 0, 0,
+		3, jiffies_delta_to_clock_t(delta), 0, 0, 0, 0,
 		atomic_read(&tw->tw_refcnt), tw, len);
 }