diff options
| author | Guoyu Su <yss2813483011xxl@gmail.com> | 2026-03-27 23:35:07 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-04-11 14:29:27 +0200 |
| commit | d970341cfa5594614c7a6634886c7688b4f5cafd (patch) | |
| tree | 9e83c380027dff2df6159d4ab768ff0bdf729619 /net/core | |
| parent | cf838b13226f95afa74d2a354d97988bd2841aae (diff) | |
net: use skb_header_pointer() for TCPv4 GSO frag_off check
[ Upstream commit ddc748a391dd8642ba6b2e4fe22e7f2ddf84b7f0 ]
Syzbot reported a KMSAN uninit-value warning in gso_features_check()
called from netif_skb_features() [1].
gso_features_check() reads iph->frag_off to decide whether to clear
mangleid_features. Accessing the IPv4 header via ip_hdr()/inner_ip_hdr()
can rely on skb header offsets that are not always safe for direct
dereference on packets injected from PF_PACKET paths.
Use skb_header_pointer() for the TCPv4 frag_off check so the header read
is robust whether data is already linear or needs copying.
[1] https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407
Link: https://lore.kernel.org/netdev/willemdebruijn.kernel.1a9f35039caab@gmail.com/
Fixes: cbc53e08a793 ("GSO: Add GSO type for fixed IPv4 ID")
Reported-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1543a7d954d9c6d00407
Tested-by: syzbot+1543a7d954d9c6d00407@syzkaller.appspotmail.com
Signed-off-by: Guoyu Su <yss2813483011xxl@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260327153507.39742-1-yss2813483011xxl@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/dev.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index 8439bac371b7..384250c3a519 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3815,10 +3815,15 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb, * segmentation-offloads.rst). */ if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) { - struct iphdr *iph = skb->encapsulation ? - inner_ip_hdr(skb) : ip_hdr(skb); + const struct iphdr *iph; + struct iphdr _iph; + int nhoff = skb->encapsulation ? + skb_inner_network_offset(skb) : + skb_network_offset(skb); - if (!(iph->frag_off & htons(IP_DF))) + iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph); + + if (!iph || !(iph->frag_off & htons(IP_DF))) features &= ~dev->mangleid_features; } |