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In the Linux kernel, the following vulnerability has been...

Moderate severity Unreviewed Published Oct 21, 2024 to the GitHub Advisory Database • Updated Nov 8, 2024

Package

No package listed— Suggest a package

Affected versions

Unknown

Patched versions

Unknown

Description

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

netfilter: br_netfilter: fix panic with metadata_dst skb

Fix a kernel panic in the br_netfilter module when sending untagged
traffic via a VxLAN device.
This happens during the check for fragmentation in br_nf_dev_queue_xmit.

It is dependent on:

  1. the br_netfilter module being loaded;
  2. net.bridge.bridge-nf-call-iptables set to 1;
  3. a bridge with a VxLAN (single-vxlan-device) netdevice as a bridge port;
  4. untagged frames with size higher than the VxLAN MTU forwarded/flooded

When forwarding the untagged packet to the VxLAN bridge port, before
the netfilter hooks are called, br_handle_egress_vlan_tunnel is called and
changes the skb_dst to the tunnel dst. The tunnel_dst is a metadata type
of dst, i.e., skb_valid_dst(skb) is false, and metadata->dst.dev is NULL.

Then in the br_netfilter hooks, in br_nf_dev_queue_xmit, there's a check
for frames that needs to be fragmented: frames with higher MTU than the
VxLAN device end up calling br_nf_ip_fragment, which in turns call
ip_skb_dst_mtu.

The ip_dst_mtu tries to use the skb_dst(skb) as if it was a valid dst
with valid dst->dev, thus the crash.

This case was never supported in the first place, so drop the packet
instead.

PING 10.0.0.2 (10.0.0.2) from 0.0.0.0 h1-eth0: 2000(2028) bytes of data.
[ 176.291791] Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000110
[ 176.292101] Mem abort info:
[ 176.292184] ESR = 0x0000000096000004
[ 176.292322] EC = 0x25: DABT (current EL), IL = 32 bits
[ 176.292530] SET = 0, FnV = 0
[ 176.292709] EA = 0, S1PTW = 0
[ 176.292862] FSC = 0x04: level 0 translation fault
[ 176.293013] Data abort info:
[ 176.293104] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
[ 176.293488] CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[ 176.293787] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[ 176.293995] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000043ef5000
[ 176.294166] [0000000000000110] pgd=0000000000000000,
p4d=0000000000000000
[ 176.294827] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
[ 176.295252] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel veth
br_netfilter bridge stp llc ipv6 crct10dif_ce
[ 176.295923] CPU: 0 PID: 188 Comm: ping Not tainted
6.8.0-rc3-g5b3fbd61b9d1 #2
[ 176.296314] Hardware name: linux,dummy-virt (DT)
[ 176.296535] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS
BTYPE=--)
[ 176.296808] pc : br_nf_dev_queue_xmit+0x390/0x4ec [br_netfilter]
[ 176.297382] lr : br_nf_dev_queue_xmit+0x2ac/0x4ec [br_netfilter]
[ 176.297636] sp : ffff800080003630
[ 176.297743] x29: ffff800080003630 x28: 0000000000000008 x27:
ffff6828c49ad9f8
[ 176.298093] x26: ffff6828c49ad000 x25: 0000000000000000 x24:
00000000000003e8
[ 176.298430] x23: 0000000000000000 x22: ffff6828c4960b40 x21:
ffff6828c3b16d28
[ 176.298652] x20: ffff6828c3167048 x19: ffff6828c3b16d00 x18:
0000000000000014
[ 176.298926] x17: ffffb0476322f000 x16: ffffb7e164023730 x15:
0000000095744632
[ 176.299296] x14: ffff6828c3f1c880 x13: 0000000000000002 x12:
ffffb7e137926a70
[ 176.299574] x11: 0000000000000001 x10: ffff6828c3f1c898 x9 :
0000000000000000
[ 176.300049] x8 : ffff6828c49bf070 x7 : 0008460f18d5f20e x6 :
f20e0100bebafeca
[ 176.300302] x5 : ffff6828c7f918fe x4 : ffff6828c49bf070 x3 :
0000000000000000
[ 176.300586] x2 : 0000000000000000 x1 : ffff6828c3c7ad00 x0 :
ffff6828c7f918f0
[ 176.300889] Call trace:
[ 176.301123] br_nf_dev_queue_xmit+0x390/0x4ec [br_netfilter]
[ 176.301411] br_nf_post_routing+0x2a8/0x3e4 [br_netfilter]
[ 176.301703] nf_hook_slow+0x48/0x124
[ 176.302060] br_forward_finish+0xc8/0xe8 [bridge]
[ 176.302371] br_nf_hook_thresh+0x124/0x134 [br_netfilter]
[ 176.302605] br_nf_forward_finish+0x118/0x22c [br_netfilter]
[ 176.302824] br_nf_forward_ip.part.0+0x264/0x290 [br_netfilter]
[ 176.303136] br_nf_forward+0x2b8/0x4e0 [br_netfilter]
[ 176.303359] nf_hook_slow+0x48/0x124
[ 176.303
---truncated---

References

Published by the National Vulnerability Database Oct 21, 2024
Published to the GitHub Advisory Database Oct 21, 2024
Last updated Nov 8, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS score

0.042%
(5th percentile)

Weaknesses

CVE ID

CVE-2024-50045

GHSA ID

GHSA-5hwh-9gc5-fwwg

Source code

No known source code

Dependabot alerts are not supported on this advisory because it does not have a package from a supported ecosystem with an affected and fixed version.

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