[FIB]: Avoid using static variables without proper locking

fib_trie_seq_show() uses two helper functions, rtn_scope() and
rtn_type() that can write to static storage without locking.

Just pass to them a temporary buffer to avoid potential corruption
(probably not triggerable but still...)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 10 deletions

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 18fb73958a49..72c78c2209d5 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2284,10 +2284,8 @@ static void seq_indent(struct seq_file *seq, int n)
         while (n-- > 0) seq_puts(seq, "   ");
 }
 
-static inline const char *rtn_scope(enum rt_scope_t s)
+static inline const char *rtn_scope(char *buf, size_t len, enum rt_scope_t s)
 {
-        static char buf[32];
-
         switch (s) {
         case RT_SCOPE_UNIVERSE: return "universe";
         case RT_SCOPE_SITE:     return "site";
@@ -2295,7 +2293,7 @@ static inline const char *rtn_scope(enum rt_scope_t s)
         case RT_SCOPE_HOST:     return "host";
         case RT_SCOPE_NOWHERE:  return "nowhere";
         default:
-                snprintf(buf, sizeof(buf), "scope=%d", s);
+                snprintf(buf, len, "scope=%d", s);
                 return buf;
         }
 }
@@ -2315,13 +2313,11 @@ static const char *rtn_type_names[__RTN_MAX] = {
         [RTN_XRESOLVE] = "XRESOLVE",
 };
 
-static inline const char *rtn_type(unsigned t)
+static inline const char *rtn_type(char *buf, size_t len, unsigned t)
 {
-        static char buf[32];
-
         if (t < __RTN_MAX && rtn_type_names[t])
                 return rtn_type_names[t];
-        snprintf(buf, sizeof(buf), "type %u", t);
+        snprintf(buf, len, "type %u", t);
         return buf;
 }
 
@@ -2359,13 +2355,19 @@ static int fib_trie_seq_show(struct seq_file *seq, void *v)
                 seq_printf(seq, "  |-- %d.%d.%d.%d\n", NIPQUAD(val));
                 for (i = 32; i >= 0; i--) {
                         struct leaf_info *li = find_leaf_info(l, i);
+
                         if (li) {
                                 struct fib_alias *fa;
+
                                 list_for_each_entry_rcu(fa, &li->falh, fa_list) {
+                                        char buf1[32], buf2[32];
+
                                         seq_indent(seq, iter->depth+1);
                                         seq_printf(seq, "  /%d %s %s", i,
-                                                   rtn_scope(fa->fa_scope),
-                                                   rtn_type(fa->fa_type));
+                                                   rtn_scope(buf1, sizeof(buf1),
+                                                             fa->fa_scope),
+                                                   rtn_type(buf2, sizeof(buf2),
+                                                             fa->fa_type));
                                         if (fa->fa_tos)
                                                 seq_printf(seq, "tos =%d\n",
                                                            fa->fa_tos);