Bug 2334531 (CVE-2024-56636)

Summary: CVE-2024-56636 kernel: geneve: do not assume mac header is set in geneve_xmit_skb()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Geneve tunneling implementation of the Linux kernel. In the geneve_xmit_skb() function, the kernel incorrectly assumes that the MAC header is set, leading to invalid memory access when it is not. This issue can be triggered when sending packets through a Geneve tunnel, resulting in warnings or crashes. A local attacker could exploit this by crafting specific network traffic to cause a denial of service, affecting system availability.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2024-12-27 16:01:40 UTC 
In the Linux kernel, the following vulnerability has been resolved:

geneve: do not assume mac header is set in geneve_xmit_skb()

We should not assume mac header is set in output path.

Use skb_eth_hdr() instead of eth_hdr() to fix the issue.

sysbot reported the following :

 WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 skb_mac_header include/linux/skbuff.h:3052 [inline]
 WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 eth_hdr include/linux/if_ether.h:24 [inline]
 WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 geneve_xmit_skb drivers/net/geneve.c:898 [inline]
 WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 geneve_xmit+0x4c38/0x5730 drivers/net/geneve.c:1039
Modules linked in:
CPU: 0 UID: 0 PID: 11635 Comm: syz.4.1423 Not tainted 6.12.0-syzkaller-10296-gaaf20f870da0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
 RIP: 0010:skb_mac_header include/linux/skbuff.h:3052 [inline]
 RIP: 0010:eth_hdr include/linux/if_ether.h:24 [inline]
 RIP: 0010:geneve_xmit_skb drivers/net/geneve.c:898 [inline]
 RIP: 0010:geneve_xmit+0x4c38/0x5730 drivers/net/geneve.c:1039
Code: 21 c6 02 e9 35 d4 ff ff e8 a5 48 4c fb 90 0f 0b 90 e9 fd f5 ff ff e8 97 48 4c fb 90 0f 0b 90 e9 d8 f5 ff ff e8 89 48 4c fb 90 <0f> 0b 90 e9 41 e4 ff ff e8 7b 48 4c fb 90 0f 0b 90 e9 cd e7 ff ff
RSP: 0018:ffffc90003b2f870 EFLAGS: 00010283
RAX: 000000000000037a RBX: 000000000000ffff RCX: ffffc9000dc3d000
RDX: 0000000000080000 RSI: ffffffff86428417 RDI: 0000000000000003
RBP: ffffc90003b2f9f0 R08: 0000000000000003 R09: 000000000000ffff
R10: 000000000000ffff R11: 0000000000000002 R12: ffff88806603c000
R13: 0000000000000000 R14: ffff8880685b2780 R15: 0000000000000e23
FS:  00007fdc2deed6c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30a1dff8 CR3: 0000000056b8c000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  __netdev_start_xmit include/linux/netdevice.h:5002 [inline]
  netdev_start_xmit include/linux/netdevice.h:5011 [inline]
  __dev_direct_xmit+0x58a/0x720 net/core/dev.c:4490
  dev_direct_xmit include/linux/netdevice.h:3181 [inline]
  packet_xmit+0x1e4/0x360 net/packet/af_packet.c:285
  packet_snd net/packet/af_packet.c:3146 [inline]
  packet_sendmsg+0x2700/0x5660 net/packet/af_packet.c:3178
  sock_sendmsg_nosec net/socket.c:711 [inline]
  __sock_sendmsg net/socket.c:726 [inline]
  __sys_sendto+0x488/0x4f0 net/socket.c:2197
  __do_sys_sendto net/socket.c:2204 [inline]
  __se_sys_sendto net/socket.c:2200 [inline]
  __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2200
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Comment 1 Avinash Hanwate 2024-12-28 03:43:24 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2024122735-CVE-2024-56636-cdeb@gregkh/T