[PATCH net 0/4] net: trust-after-modification fixes for IPv4 options + netlabel

[Qi Tang <tpluszz77@gmail.com>]

Four small bounds-check fixes for a recurring pattern in IPv4 options
and CIPSO/CALIPSO consumers.  The parse-time validator stores only
the option offset into IPCB / skb metadata.  Later consumers (cmsg
echo, mrouted report, netlabel getattr) re-read the length /
pointer / cat_len bytes from the skb body and use them for indexed
memcpy or bitmap walk.  An nftables payload mutation reachable from
an unprivileged user namespace (CAP_NET_ADMIN inside the namespace)
rewrites those bytes between parse and consume.

  1/4 __ip_options_echo()                40-byte stack OOB write
                                         (KASAN: stack-out-of-bounds,
                                         Write of size 255).
  2/4 ipmr_cache_report()                Up to 40-byte OOB read of
                                         skb head leaked into the
                                         IGMPMSG cmsg delivered to
                                         mrouted.
  3/4 netlbl_skbuff_getattr() / CALIPSO  ~232-byte slab OOB read
                                         driving SELinux/Smack MLS
                                         category bitmap.
  4/4 netlbl_skbuff_getattr() / CIPSO    Sibling of 3/4 on the
                                         AF_INET (CIPSO IPv4) path.

Qi Tang (4):
  ipv4: validate ip_options length in __ip_options_echo() against skb
    tail
  ipv4: ipmr: clamp ip_hdrlen against skb_headlen in ipmr_cache_report
  netlabel: validate CALIPSO option against skb tail in
    netlbl_skbuff_getattr
  netlabel: validate CIPSO option against skb tail in
    netlbl_skbuff_getattr

 net/ipv4/ip_options.c        |  8 ++++++++
 net/ipv4/ipmr.c              |  2 +-
 net/netlabel/netlabel_kapi.c | 27 +++++++++++++++++++++++----
 3 files changed, 32 insertions(+), 5 deletions(-)

-- 
2.47.3