CVE-2024-35971 Affecting kernel-syms-azure package, versions <6.4.0-150600.8.5.1
Threat Intelligence
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Test your applications- Snyk IDSNYK-SLES156-KERNELSYMSAZURE-7347535
- published22 Jun 2024
- disclosed21 Jun 2024
Introduced: 21 Jun 2024
CVE-2024-35971 (opens in a new tab)How to fix?
Upgrade SLES:15.6 kernel-syms-azure to version 6.4.0-150600.8.5.1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-syms-azure package and not the kernel-syms-azure package as distributed by SLES.
See How to fix? for SLES:15.6 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
net: ks8851: Handle softirqs at the end of IRQ thread to fix hang
The ks8851_irq() thread may call ks8851_rx_pkts() in case there are any packets in the MAC FIFO, which calls netif_rx(). This netif_rx() implementation is guarded by local_bh_disable() and local_bh_enable(). The local_bh_enable() may call do_softirq() to run softirqs in case any are pending. One of the softirqs is net_rx_action, which ultimately reaches the driver .start_xmit callback. If that happens, the system hangs. The entire call chain is below:
ks8851_start_xmit_par from netdev_start_xmit netdev_start_xmit from dev_hard_start_xmit dev_hard_start_xmit from sch_direct_xmit sch_direct_xmit from __dev_queue_xmit __dev_queue_xmit from __neigh_update __neigh_update from neigh_update neigh_update from arp_process.constprop.0 arp_process.constprop.0 from __netif_receive_skb_one_core __netif_receive_skb_one_core from process_backlog process_backlog from __napi_poll.constprop.0 __napi_poll.constprop.0 from net_rx_action net_rx_action from __do_softirq __do_softirq from call_with_stack call_with_stack from do_softirq do_softirq from __local_bh_enable_ip __local_bh_enable_ip from netif_rx netif_rx from ks8851_irq ks8851_irq from irq_thread_fn irq_thread_fn from irq_thread irq_thread from kthread kthread from ret_from_fork
The hang happens because ks8851_irq() first locks a spinlock in ks8851_par.c ks8851_lock_par() spin_lock_irqsave(&ksp->lock, ...) and with that spinlock locked, calls netif_rx(). Once the execution reaches ks8851_start_xmit_par(), it calls ks8851_lock_par() again which attempts to claim the already locked spinlock again, and the hang happens.
Move the do_softirq() call outside of the spinlock protected section of ks8851_irq() by disabling BHs around the entire spinlock protected section of ks8851_irq() handler. Place local_bh_enable() outside of the spinlock protected section, so that it can trigger do_softirq() without the ks8851_par.c ks8851_lock_par() spinlock being held, and safely call ks8851_start_xmit_par() without attempting to lock the already locked spinlock.
Since ks8851_irq() is protected by local_bh_disable()/local_bh_enable() now, replace netif_rx() with __netif_rx() which is not duplicating the local_bh_disable()/local_bh_enable() calls.
References
- https://www.suse.com/security/cve/CVE-2024-35971.html
- https://bugzilla.suse.com/1224578
- http://www.openwall.com/lists/oss-security/2024/05/30/1
- http://www.openwall.com/lists/oss-security/2024/05/30/2
- https://git.kernel.org/stable/c/492337a4fbd1421b42df684ee9b34be2a2722540
- https://git.kernel.org/stable/c/49d5d70538b6b8f2a3f8f1ac30c1f921d4a0929b
- https://git.kernel.org/stable/c/be0384bf599cf1eb8d337517feeb732d71f75a6f
- https://git.kernel.org/stable/c/cba376eb036c2c20077b41d47b317d8218fe754f