From 5d2d3f2300c37f2a8e6d5b1161239cff98c82daf Mon Sep 17 00:00:00 2001 From: Alex Henrie Date: Thu, 31 Aug 2023 22:41:27 -0600 Subject: [PATCH] net: ipv6/addrconf: avoid integer underflow in ipv6_create_tempaddr [ Upstream commit f31867d0d9d82af757c1e0178b659438f4c1ea3c ] The existing code incorrectly casted a negative value (the result of a subtraction) to an unsigned value without checking. For example, if /proc/sys/net/ipv6/conf/*/temp_prefered_lft was set to 1, the preferred lifetime would jump to 4 billion seconds. On my machine and network the shortest lifetime that avoided underflow was 3 seconds. Fixes: 76506a986dc3 ("IPv6: fix DESYNC_FACTOR") Signed-off-by: Alex Henrie Reviewed-by: David Ahern Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/ipv6/addrconf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 0c0b7969840f..6572174e2115 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -1368,7 +1368,7 @@ retry: * idev->desync_factor if it's larger */ cnf_temp_preferred_lft = READ_ONCE(idev->cnf.temp_prefered_lft); - max_desync_factor = min_t(__u32, + max_desync_factor = min_t(long, idev->cnf.max_desync_factor, cnf_temp_preferred_lft - regen_advance);