From 172db56d90d29e47e7d0d64885d5dbd92c87ec42 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 6 Dec 2023 12:59:07 -0800 Subject: [PATCH] netlink: Return unsigned value for nla_len() The return value from nla_len() is never expected to be negative, and can never be more than struct nlattr::nla_len (a u16). Adjust the prototype on the function. This will let GCC's value range optimization passes know that the return can never be negative, and can never be larger than u16. As recently discussed[1], this silences the following warning in GCC 12+: net/wireless/nl80211.c: In function 'nl80211_set_cqm_rssi.isra': net/wireless/nl80211.c:12892:17: warning: 'memcpy' specified bound 18446744073709551615 exceeds maximum object size 9223372036854775807 [-Wstringop-overflow=] 12892 | memcpy(cqm_config->rssi_thresholds, thresholds, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 12893 | flex_array_size(cqm_config, rssi_thresholds, | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 12894 | n_thresholds)); | ~~~~~~~~~~~~~~ A future change would be to clamp the subtraction to make sure it never wraps around if nla_len is somehow less than NLA_HDRLEN, which would have the additional benefit of being defensive in the face of nlattr corruption or logic errors. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202311090752.hWcJWAHL-lkp@intel.com/ [1] Cc: Johannes Berg Cc: Jeff Johnson Cc: Michael Walle Cc: Max Schulze Link: https://lore.kernel.org/r/20231202202539.it.704-kees@kernel.org Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20231206205904.make.018-kees@kernel.org Signed-off-by: Jakub Kicinski --- include/net/netlink.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/net/netlink.h b/include/net/netlink.h index 167b91348e57..28039e57070a 100644 --- a/include/net/netlink.h +++ b/include/net/netlink.h @@ -1214,7 +1214,7 @@ static inline void *nla_data(const struct nlattr *nla) * nla_len - length of payload * @nla: netlink attribute */ -static inline int nla_len(const struct nlattr *nla) +static inline u16 nla_len(const struct nlattr *nla) { return nla->nla_len - NLA_HDRLEN; }