Affected: Linux

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

net/core: Fix ETH_P_1588 flow dissector

When a PTP ethernet raw frame with a size of more than 256 bytes followed by a 0xff pattern is sent to __skb_flow_dissect, nhoff value calculation is wrong. For example: hdr->message_length takes the wrong value (0xffff) and it does not replicate real header length. In this case, 'nhoff' value was overridden and the PTP header was badly dissected. This leads to a kernel crash.

net/core: flow_dissector net/core flow dissector nhoff = 0x0000000e net/core flow dissector hdr->message_length = 0x0000ffff net/core flow dissector nhoff = 0x0001000d (u16 overflow) ... skb linear: 00000000: 00 a0 c9 00 00 00 00 a0 c9 00 00 00 88 skb frag: 00000000: f7 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

Using the size of the ptp_header struct will allow the corrected calculation of the nhoff value.

net/core flow dissector nhoff = 0x0000000e net/core flow dissector nhoff = 0x00000030 (sizeof ptp_header) ... skb linear: 00000000: 00 a0 c9 00 00 00 00 a0 c9 00 00 00 88 f7 ff ff skb linear: 00000010: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff skb linear: 00000020: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff skb frag: 00000000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

Kernel trace: [ 74.984279] ------------[ cut here ]------------ [ 74.989471] kernel BUG at include/linux/skbuff.h:2440! [ 74.995237] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI [ 7…