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Merge branch 'net-two-fixes-for-qdisc_pkt_len_init'

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Eric Dumazet says:

====================
net: two fixes for qdisc_pkt_len_init()

Inspired by one syzbot report.

At least one qdisc (fq_codel) depends on qdisc_skb_cb(skb)->pkt_len
having a sane value (not zero)

With the help of af_packet, syzbot was able to fool qdisc_pkt_len_init()
to precisely set qdisc_skb_cb(skb)->pkt_len to zero.

First patch fixes this issue.

Second one (a separate one to help future bisections) adds
more sanity check to SKB_GSO_DODGY users.
====================

Link: https://patch.msgid.link/20240924150257.1059524-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Paolo Abeni
2024-10-01 11:47:08 +02:00
parent e9d591b16c ab9a9a9e96
commit 23e19f2473
1 changed files with 8 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/core/dev.c
+8 -4
View File
@@ -3758,7 +3758,7 @@ static void qdisc_pkt_len_init(struct sk_buff *skb)
sizeof(_tcphdr), &_tcphdr);
if (likely(th))
hdr_len += __tcp_hdrlen(th);
} else {
} else if (shinfo->gso_type & SKB_GSO_UDP_L4) {
struct udphdr _udphdr;
if (skb_header_pointer(skb, hdr_len,
@@ -3766,10 +3766,14 @@ static void qdisc_pkt_len_init(struct sk_buff *skb)
hdr_len += sizeof(struct udphdr);
}
if (shinfo->gso_type & SKB_GSO_DODGY)
gso_segs = DIV_ROUND_UP(skb->len - hdr_len,
shinfo->gso_size);
if (unlikely(shinfo->gso_type & SKB_GSO_DODGY)) {
int payload = skb->len - hdr_len;
/* Malicious packet. */
if (payload <= 0)
return;
gso_segs = DIV_ROUND_UP(payload, shinfo->gso_size);
}
qdisc_skb_cb(skb)->pkt_len += (gso_segs - 1) * hdr_len;
}
}