Linux Kernel up to 6.7.1 netdev_priv null pointer dereference

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.7.1 and classified as critical. The impacted element is the function netdev_priv. This manipulation causes null pointer dereference. This vulnerability is registered as CVE-2024-26596. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.7.1 (Operating System). It has been declared as critical. Affected by this vulnerability is the function netdev_priv. The manipulation with an unknown input leads to a null pointer dereference vulnerability. The CWE definition for the vulnerability is CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: net: dsa: fix netdev_priv() dereference before check on non-DSA netdevice events After the blamed commit, we started doing this dereference for every NETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER event in the system. static inline struct dsa_port *dsa_user_to_port(const struct net_device *dev) { struct dsa_user_priv *p = netdev_priv(dev); return p->dp; } Which is obviously bogus, because not all net_devices have a netdev_priv() of type struct dsa_user_priv. But struct dsa_user_priv is fairly small, and p->dp means dereferencing 8 bytes starting with offset 16. Most drivers allocate that much private memory anyway, making our access not fault, and we discard the bogus data quickly afterwards, so this wasn't caught. But the dummy interface is somewhat special in that it calls alloc_netdev() with a priv size of 0. So every netdev_priv() dereference is invalid, and we get this when we emit a NETDEV_PRECHANGEUPPER event with a VLAN as its new upper: $ ip link add dummy1 type dummy $ ip link add link dummy1 name dummy1.100 type vlan id 100 [ 43.309174] ================================================================== [ 43.316456] BUG: KASAN: slab-out-of-bounds in dsa_user_prechangeupper+0x30/0xe8 [ 43.323835] Read of size 8 at addr ffff3f86481d2990 by task ip/374 [ 43.330058] [ 43.342436] Call trace: [ 43.366542] dsa_user_prechangeupper+0x30/0xe8 [ 43.371024] dsa_user_netdevice_event+0xb38/0xee8 [ 43.375768] notifier_call_chain+0xa4/0x210 [ 43.379985] raw_notifier_call_chain+0x24/0x38 [ 43.384464] __netdev_upper_dev_link+0x3ec/0x5d8 [ 43.389120] netdev_upper_dev_link+0x70/0xa8 [ 43.393424] register_vlan_dev+0x1bc/0x310 [ 43.397554] vlan_newlink+0x210/0x248 [ 43.401247] rtnl_newlink+0x9fc/0xe30 [ 43.404942] rtnetlink_rcv_msg+0x378/0x580 Avoid the kernel oops by dereferencing after the type check, as customary.

The weakness was published 02/23/2024. It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2024-26596 since 02/19/2024. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 213018 (SUSE SLES15 / openSUSE 15 Security Update : kernel (SUSE-SU-2024:4314-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.7.2 or 6.8-rc1 eliminates this vulnerability. Applying the patch dbd909c20c11/844f104790bd is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (213018). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.7.0
• 6.7.1

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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