CVE-2020-36789: In the Linux kernel, the following vulnerability has been resolved: can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard IRQ context If a driver…

PriorityP422medium5.5CVSS 3.1

AVLACLPRLUINSUCNINAH

EPSS

0.18%

7.4th percentile

In the Linux kernel, the following vulnerability has been resolved: can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard IRQ context If a driver calls can_get_echo_skb() during a hardware IRQ (which is often, but not always, the case), the 'WARN_ON(in_irq)' in net/core/skbuff.c#skb_release_head_state() might be triggered, under network congestion circumstances, together with the potential risk of a NULL pointer dereference. The root cause of this issue is the call to kfree_skb() instead of dev_kfree_skb_irq() in net/core/dev.c#enqueue_to_backlog(). This patch prevents the skb to be freed within the call to netif_rx() by incrementing its reference count with skb_get(). The skb is finally freed by one of the in-irq-context safe functions: dev_consume_skb_any() or dev_kfree_skb_any(). The "any" version is used because some drivers might call can_get_echo_skb() in a normal context. The reason for this issue to occur is that initially, in the core network stack, loopback skb were not supposed to be received in hardware IRQ context. The CAN stack is an exeption. This bug was previously reported back in 2017 in [1] but the proposed patch never got accepted. While [1] directly modifies net/core/dev.c, we try to propose here a smoother modification local to CAN network stack (the assumption behind is that only CAN devices are affected by this issue). [1] http://lore.kernel.org/r/[email protected]

Affected

20 ranges

Vendor	Product	Version range	Fixed in
debian	linux	< linux 5.9.9-1 (bookworm)	linux 5.9.9-1 (bookworm)
linux	linux	—	—
linux	linux	>= 39549eef3587f1c1e8c65c88a2400d10fd30ea17 < 248b71ce92d4f3a574b2537f9838f48e892618f4	248b71ce92d4f3a574b2537f9838f48e892618f4
linux	linux	>= 39549eef3587f1c1e8c65c88a2400d10fd30ea17 < 451187b20431924d13fcfecc500d7cd2d9951bac	451187b20431924d13fcfecc500d7cd2d9951bac
linux	linux	>= 39549eef3587f1c1e8c65c88a2400d10fd30ea17 < 3a922a85701939624484e7f2fd07d32beed00d25	3a922a85701939624484e7f2fd07d32beed00d25
linux	linux	>= 39549eef3587f1c1e8c65c88a2400d10fd30ea17 < 7e4cf2ec0ca236c3e5f904239cec6efe1f3baf22	7e4cf2ec0ca236c3e5f904239cec6efe1f3baf22
linux	linux	>= 39549eef3587f1c1e8c65c88a2400d10fd30ea17 < ab46748bf98864f9c3f5559060bf8caf9df2b41e	ab46748bf98864f9c3f5559060bf8caf9df2b41e
linux	linux	>= 39549eef3587f1c1e8c65c88a2400d10fd30ea17 < 87530b557affe01c764de32dbeb58cdf47234574	87530b557affe01c764de32dbeb58cdf47234574
linux	linux	>= 39549eef3587f1c1e8c65c88a2400d10fd30ea17 < 2283f79b22684d2812e5c76fc2280aae00390365	2283f79b22684d2812e5c76fc2280aae00390365
linux	linux_kernel	—	—
linux	linux_kernel	>= 0 < 5.9.9-1	5.9.9-1
linux	linux_kernel	>= 0 < 5.9.9-1	5.9.9-1
linux	linux_kernel	>= 0 < 5.9.9-1	5.9.9-1
linux	linux_kernel	>= 0 < 5.9.9-1	5.9.9-1
linux	linux_kernel	>= 2.6.31 < 4.4.244	4.4.244
linux	linux_kernel	>= 4.10 < 4.14.207	4.14.207
linux	linux_kernel	>= 4.15 < 4.19.158	4.19.158
linux	linux_kernel	>= 4.20 < 5.4.78	5.4.78
linux	linux_kernel	>= 4.5 < 4.9.244	4.9.244
linux	linux_kernel	>= 5.5 < 5.9.9	5.9.9

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

osv5.5MEDIUM

vendor_debian5.5MEDIUM

vendor_redhat5.5MEDIUM

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