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, 3 insertions, 6 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index c66b90f71c9b..aa41b0e6b163 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1875,7 +1875,7 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
                    tp->write_seq-tp->snd_una,
                    (sp->sk_state == TCP_LISTEN) ? sp->sk_ack_backlog : (tp->rcv_nxt - tp->copied_seq),
                    timer_active,
-                   jiffies_to_clock_t(timer_expires - jiffies),
+                   jiffies_delta_to_clock_t(timer_expires - jiffies),
                    icsk->icsk_retransmits,
                    sock_i_uid(sp),
                    icsk->icsk_probes_out,
@@ -1895,10 +1895,7 @@ static void get_timewait6_sock(struct seq_file *seq,
         const struct in6_addr *dest, *src;
         __u16 destp, srcp;
         const struct inet6_timewait_sock *tw6 = inet6_twsk((struct sock *)tw);
-        int ttd = tw->tw_ttd - jiffies;
-
-        if (ttd < 0)
-                ttd = 0;
+        long delta = tw->tw_ttd - jiffies;
 
         dest = &tw6->tw_v6_daddr;
         src  = &tw6->tw_v6_rcv_saddr;
@@ -1914,7 +1911,7 @@ static void get_timewait6_sock(struct seq_file *seq,
                    dest->s6_addr32[0], dest->s6_addr32[1],
                    dest->s6_addr32[2], dest->s6_addr32[3], 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);
 }