netfilter: qtaguid: fix proc/.../stats uid filtered output

"cat /proc/net/xt_qtaguid/stats"
for a non-priviledged UID would output multiple twice its own stats.
The fix tweaks the way lines are counted.

Non-root:
  idx iface acct_tag_hex uid_tag_int cnt_set ...
  2 wlan0 0x0 10022 0 ...
  3 wlan0 0x0 10022 1 ...
  4 wlan0 0x3010000000000000 10022 0 ...
  5 wlan0 0x3010000000000000 10022 1 ...

Root:
  idx iface acct_tag_hex uid_tag_int cnt_set
  2 wlan0 0x0 0 0 ...
  3 wlan0 0x0 0 1 ...
  4 wlan0 0x0 1000 0 ...
  ...
  12 wlan0 0x0 10022 0 ...
  13 wlan0 0x0 10022 1 ...
  ...
  18 wlan0 0x3010000000000000 10022 0 ...
  19 wlan0 0x3010000000000000 10022 1 ...

Change-Id: I3cae1f4fee616bc897831350374656b0c718c45b
Signed-off-by: JP Abgrall <jpa@google.com>

diff --git a/net/netfilter/xt_qtaguid.c b/net/netfilter/xt_qtaguid.c
index 80b5990045bc1853fd669e68ca772e6257718b32..b145f5a4b45d2d6e27e1dd7f8ef27b9b18d98c7e 100644 (file)
--- a/net/netfilter/xt_qtaguid.c
+++ b/net/netfilter/xt_qtaguid.c
@@ -1788,6 +1788,7 @@ struct proc_print_info {
        struct iface_stat *iface_entry;
        struct tag_stat *ts_entry;
        int item_index;
+       int items_to_skip;
        int char_count;
 };
 
@@ -1795,7 +1796,10 @@ static int pp_stats_line(struct proc_print_info *ppi, int cnt_set)
 {
        int len;
        struct data_counters *cnts;
+
        if (!ppi->item_index) {
+               if (ppi->item_index++ < ppi->items_to_skip)
+                       return 0;
                len = snprintf(ppi->outp, ppi->char_count,
                               "idx iface acct_tag_hex uid_tag_int cnt_set "
                               "rx_bytes rx_packets "
@@ -1809,6 +1813,7 @@ static int pp_stats_line(struct proc_print_info *ppi, int cnt_set)
        } else {
                tag_t tag = ppi->ts_entry->tn.tag;
                uid_t stat_uid = get_uid_from_tag(tag);
+
                if (!can_read_other_uid_stats(stat_uid)) {
                        CT_DEBUG("qtaguid: stats line: "
                                 "%s 0x%llx %u: "
@@ -1818,6 +1823,8 @@ static int pp_stats_line(struct proc_print_info *ppi, int cnt_set)
                                 current->pid, current_fsuid());
                        return 0;
                }
+               if (ppi->item_index++ < ppi->items_to_skip)
+                       return 0;
                cnts = &ppi->ts_entry->counters;
                len = snprintf(
                        ppi->outp, ppi->char_count,
@@ -1891,11 +1898,13 @@ static int qtaguid_stats_proc_read(char *page, char **num_items_returned,
        ppi.item_index = 0;
        ppi.char_count = char_count;
        ppi.num_items_returned = num_items_returned;
+       ppi.items_to_skip = items_to_skip;
 
        if (unlikely(module_passive)) {
                len = pp_stats_line(&ppi, 0);
                /* The header should always be shorter than the buffer. */
                WARN_ON(len >= ppi.char_count);
+               (*num_items_returned)++;
                *eof = 1;
                return len;
        }
@@ -1907,16 +1916,17 @@ static int qtaguid_stats_proc_read(char *page, char **num_items_returned,
        if (*eof)
                return 0;
 
-       if (!items_to_skip) {
-               /* The idx is there to help debug when things go belly up. */
-               len = pp_stats_line(&ppi, 0);
-               /* Don't advance the outp unless the whole line was printed */
-               if (len >= ppi.char_count) {
-                       *ppi.outp = '\0';
-                       return ppi.outp - page;
-               }
+       /* The idx is there to help debug when things go belly up. */
+       len = pp_stats_line(&ppi, 0);
+       /* Don't advance the outp unless the whole line was printed */
+       if (len >= ppi.char_count) {
+               *ppi.outp = '\0';
+               return ppi.outp - page;
+       }
+       if (len) {
                ppi.outp += len;
                ppi.char_count -= len;
+               (*num_items_returned)++;
        }
 
        spin_lock_bh(&iface_stat_list_lock);
@@ -1927,8 +1937,6 @@ static int qtaguid_stats_proc_read(char *page, char **num_items_returned,
                     node;
                     node = rb_next(node)) {
                        ppi.ts_entry = rb_entry(node, struct tag_stat, tn.node);
-                       if (ppi.item_index++ < items_to_skip)
-                               continue;
                        if (!pp_sets(&ppi)) {
                                spin_unlock_bh(
                                        &ppi.iface_entry->tag_stat_list_lock);