From: Yuejie Shi <syjcnss@gmail.com> mainline inclusion from mainline-v7.2-rc7 commit d1ad8fb2ac6a1afb71dc22d9ae8efb4dda96c824 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/18174 CVE: CVE-2026-74598 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- rt6_route_rcv() validates the Route Information option (RFC 4191) length against the prefix length, but both checks are off by one. rinfo->length is the ND option length in units of 8 octets and it *includes* the 8-byte option header, so an option carrying N bytes of prefix has length == 1 + N/8. RFC 4191 section 2.3 requires length 3 when Prefix Length is greater than 64, and 2 or 3 when it is greater than 0. The code accepts length >= 2 and length >= 1 respectively. ipv6_addr_prefix() then copies prefix_len/8 bytes out of rinfo->prefix, so a Router Advertisement with (prefix_len=128, length=2) or (prefix_len=64, length=1) makes the kernel read up to 8 bytes past the end of the option. Those bytes end up in the prefix of the route that gets installed, so they are visible to userspace: # RA with a Route Information option (prefix_len=128, length=2) # followed by a source link-layer address option, 01 01 de ad be ef ca fe $ ip -6 route show 2001:db8:dead:beef:101:dead:beef:cafe via fe80::1234 dev veth0 proto ra ^^^^^^^^^^^^^^^^^^ the next option, read out of bounds When the Route Information option is the last one in the packet, those eight bytes come from the skb tail room instead. Reject the option lengths RFC 4191 does not allow. Fixes: 70ceb4f53929 ("[IPV6]: ROUTE: Add experimental support for Route Information Option in RA (RFC4191).") Cc: stable@vger.kernel.org Signed-off-by: Yuejie Shi <syjcnss@gmail.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Link: https://patch.msgid.link/20260730035310.74584-1-syjcnss@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: JiangJieHua <jiangjiehua1@huawei.com> --- net/ipv6/route.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 907a5e5078199..e806ddc33c259 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -821,13 +821,13 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len, } else if (rinfo->prefix_len > 128) { return -EINVAL; } else if (rinfo->prefix_len > 64) { - if (rinfo->length < 2) { + /* RFC 4191: Length MUST be 3 when Prefix Length > 64 */ + if (rinfo->length < 3) return -EINVAL; - } } else if (rinfo->prefix_len > 0) { - if (rinfo->length < 1) { + /* RFC 4191: Length MUST be 2 or 3 when Prefix Length > 0 */ + if (rinfo->length < 2) return -EINVAL; - } } pref = rinfo->route_pref; -- 2.33.8