CVE-2025-37749 — net: ppp: Add bound checking for skb data on ppp_sync_txmung

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

net: ppp: Add bound checking for skb data on ppp_sync_txmung

Ensure we have enough data in linear buffer from skb before accessing initial bytes. This prevents potential out-of-bounds accesses when processing short packets.

When ppp_sync_txmung receives an incoming package with an empty payload: (remote) gef➤ p *(struct pppoe_hdr *) (skb->head + skb->network_header) $18 = { type = 0x1, ver = 0x1, code = 0x0, sid = 0x2, length = 0x0, tag = 0xffff8880371cdb96 }

from the skb struct (trimmed) tail = 0x16, end = 0x140, head = 0xffff88803346f400 "4", data = 0xffff88803346f416 ":\377", truesize = 0x380, len = 0x0, data_len = 0x0, mac_len = 0xe, hdr_len = 0x0,

it is not safe to access data[2].

[pabeni@redhat.com: fixed subj typo]

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CVE-2025-37749 — net: ppp: Add bound checking for skb data on ppp_sync_txmung