Bug 2031194 (CVE-2021-4095) - CVE-2021-4095 kernel: KVM: NULL pointer dereference in kvm_dirty_ring_get() in virt/kvm/dirty_ring.c
Summary: CVE-2021-4095 kernel: KVM: NULL pointer dereference in kvm_dirty_ring_get() i...
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2021-4095
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2031195
Blocks: Embargoed2026458 Red Hat2031196
TreeView+ depends on / blocked
 
Reported: 2021-12-10 18:20 UTC by Guilherme de Almeida Suckevicz
Modified: 2022-08-03 09:43 UTC (History)
48 users (show)

Fixed In Version: kernel 5.17
Doc Type: If docs needed, set a value
Doc Text:
A NULL pointer dereference was found in the Linux kernel's KVM when dirty ring logging is enabled without an active vCPU context. An unprivileged local attacker on the host may use this flaw to cause a kernel oops condition and thus a denial of service by issuing a KVM_XEN_HVM_SET_ATTR ioctl.
Clone Of:
Environment:
Last Closed: 2021-12-16 15:15:09 UTC

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Description Guilherme de Almeida Suckevicz 2021-12-10 18:20:34 UTC 
A NULL pointer dereference in kvm_dirty_ring_get() in virt/kvm/dirty_ring.c via a KVM KVM_XEN_HVM_SET_ATTR ioctl when there is no vCPU created.

References:
https://lore.kernel.org/kvm/CAFcO6XOmoS7EacN_n6v4Txk7xL7iqRa2gABg3F7E3Naf5uG94g@mail.gmail.com/
https://patchwork.kernel.org/project/kvm/patch/20211121125451.9489-12-dwmw2@infradead.org/
Comment 1 Guilherme de Almeida Suckevicz 2021-12-10 18:21:26 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 2031195]
Comment 4 Mauro Matteo Cascella 2022-01-17 11:31:24 UTC 
The patch for this issue is now available upstream:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=55749769fe608fa3f4a075e42e89d237c8e37637
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