Re: [5/9] [TUN] Fix check for underflow

[Patrick McHardy]

Chris Wright wrote:
> -stable review patch.  If anyone has any objections, please let us know.

I agree to both patches and additionally propose this one.
It fixes a crash when reading /proc/net/route (netstat -rn)
while routes are changed. I've seen two bugreports of users
beeing hit by this bug, one for 2.6.10, one for 2.6.11.

Regards
Patrick
# This is a BitKeeper generated diff -Nru style patch.
#
# ChangeSet
#   2005/03/10 18:20:44-08:00 kaber@xxxxxxxxx 
#   [IPV4]: Fix crash while reading /proc/net/route caused by stale pointers
#   
#   Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
#   Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
# 
# net/ipv4/fib_hash.c
#   2005/03/10 18:20:30-08:00 kaber@xxxxxxxxx +11 -1
#   [IPV4]: Fix crash while reading /proc/net/route caused by stale pointers
#   
#   Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
#   Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
# 
diff -Nru a/net/ipv4/fib_hash.c b/net/ipv4/fib_hash.c
--- a/net/ipv4/fib_hash.c	2005-03-17 00:58:42 +01:00
+++ b/net/ipv4/fib_hash.c	2005-03-17 00:58:42 +01:00
@@ -919,13 +919,23 @@
 	return fa;
 }
 
+static struct fib_alias *fib_get_idx(struct seq_file *seq, loff_t pos)
+{
+	struct fib_alias *fa = fib_get_first(seq);
+
+	if (fa)
+		while (pos && (fa = fib_get_next(seq)))
+			--pos;
+	return pos ? NULL : fa;
+}
+
 static void *fib_seq_start(struct seq_file *seq, loff_t *pos)
 {
 	void *v = NULL;
 
 	read_lock(&fib_hash_lock);
 	if (ip_fib_main_table)
-		v = *pos ? fib_get_next(seq) : SEQ_START_TOKEN;
+		v = *pos ? fib_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
 	return v;
 }