CVE-2024-26861

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

wireguard: receive: annotate data-race around receiving_counter.counter

Syzkaller with KCSAN identified a data-race issue when accessing keypair->receiving_counter.counter. Use READ_ONCE() and WRITE_ONCE() annotations to mark the data race as intentional.

BUG: KCSAN: data-race in wg_packet_decrypt_worker / wg_packet_rx_poll

write to 0xffff888107765888 of 8 bytes by interrupt on cpu 0:
 counter_validate drivers/net/wireguard/receive.c:321 [inline]
 wg_packet_rx_poll+0x3ac/0xf00 drivers/net/wireguard/receive.c:461
 __napi_poll+0x60/0x3b0 net/core/dev.c:6536
 napi_poll net/core/dev.c:6605 [inline]
 net_rx_action+0x32b/0x750 net/core/dev.c:6738
 __do_softirq+0xc4/0x279 kernel/softirq.c:553
 do_softirq+0x5e/0x90 kernel/softirq.c:454
 __local_bh_enable_ip+0x64/0x70 kernel/softirq.c:381
 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:167 [inline]
 _raw_spin_unlock_bh+0x36/0x40 kernel/locking/spinlock.c:210
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 ptr_ring_consume_bh include/linux/ptr_ring.h:367 [inline]
 wg_packet_decrypt_worker+0x6c5/0x700 drivers/net/wireguard/receive.c:499
 process_one_work kernel/workqueue.c:2633 [inline]
 ...

read to 0xffff888107765888 of 8 bytes by task 3196 on cpu 1:
 decrypt_packet drivers/net/wireguard/receive.c:252 [inline]
 wg_packet_decrypt_worker+0x220/0x700 drivers/net/wireguard/receive.c:501
 process_one_work kernel/workqueue.c:2633 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2706
 worker_thread+0x525/0x730 kernel/workqueue.c:2787
 ...

Weakness

The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.

Affected Software

Extended Description

This can have security implications when the expected synchronization is in security-critical code, such as recording whether a user is authenticated or modifying important state information that should not be influenced by an outsider. A race condition occurs within concurrent environments, and is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. Programmers may assume that certain code sequences execute too quickly to be affected by an interfering code sequence; when they are not, this violates atomicity. For example, the single “x++” statement may appear atomic at the code layer, but it is actually non-atomic at the instruction layer, since it involves a read (the original value of x), followed by a computation (x+1), followed by a write (save the result to x). The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/3f94da807fe1668b9830f0eefbbf7e887b0a7bc6
• https://git.kernel.org/stable/c/45a83b220c83e3c326513269afbf69ae6fc65cce
• https://git.kernel.org/stable/c/78739d72f16b2d7d549f713f1dfebd678d32484b
• https://git.kernel.org/stable/c/bba045dc4d996d03dce6fe45726e78a1a1f6d4c3
• https://git.kernel.org/stable/c/d691be84ab898cf136a35176eaf2f8fc116563f0
• https://git.kernel.org/stable/c/f87884e0dffd61b47e58bc6e1e2f6843c212b0cc
• https://git.kernel.org/stable/c/fdf16de078a97bf14bb8ee2b8d47cc3d3ead09ed
• https://git.kernel.org/stable/c/3f94da807fe1668b9830f0eefbbf7e887b0a7bc6
• https://git.kernel.org/stable/c/45a83b220c83e3c326513269afbf69ae6fc65cce
• https://git.kernel.org/stable/c/78739d72f16b2d7d549f713f1dfebd678d32484b
• https://git.kernel.org/stable/c/bba045dc4d996d03dce6fe45726e78a1a1f6d4c3
• https://git.kernel.org/stable/c/d691be84ab898cf136a35176eaf2f8fc116563f0
• https://git.kernel.org/stable/c/f87884e0dffd61b47e58bc6e1e2f6843c212b0cc
• https://git.kernel.org/stable/c/fdf16de078a97bf14bb8ee2b8d47cc3d3ead09ed
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html