There is also KVM, which may handle system calls differently. Don't know.
But, the flaw is in kernel memory management. There is nothing changed "in" the system calls per se. I can't imagine how multiple instances could share the same kernel memory, or module to manipulate it.
Specifically crypto/aglif_aead.c has to be patched to change how it uses local memory. This is used by a kernel module that the system calls use.
On Fri, May 15, 2026 at 02:51:56PM -0700, Brian E. Lavender wrote:
I think your analysis to patch everywhere may be mistaken.
https://wiki.xenproject.org/wiki/Xen_FAQ_Design_and_in_Depth#How_does_Xen_pr... "Xen maintains two IDT's, one global IDT (its own) and other per domain IDT. Xen uses global IDT to register the entire trap handler except for system call handler (int 0x80). When a VM gets scheduled, its system call handler (from per domain IDT table) is registered with the processor. Hence when a domain/VM executes a system call, its own handler is executed. "
IDT - Interrupt Descriptor Table (IDT)
https://xint.io/blog/copy-fail-linux-distributions
So, the scheduler puts in the IDT for the guest. The guest does a socket open for copy/fail CVE. It seems that the socket system call will be implemented by the Xen host hypervisor. Therefore, the patched hypervisor will mark it dirty and the vulnerabiltiy mitigated.
Anybody want to try and find a contradiction?
Brian
On Sat, May 02, 2026 at 10:09:55AM -0700, Gary wrote:
It's a flaw in the kernel, so you have to patch the kernel in anything that can run a shell where you don't want privilege escalation.
Which I would think is everywhere.
Have you seen any info on patch availability or what versions of Fedora and other distros will have available patches?
I saw some instructions where you can disable a kernel module using modprobe to avoid the vulnerability. There was no information on what functionality was affected by making the change. It sounded like it reverted to doing the copy correctly, which would be a relatively easy and low impact fix.
On Fri, May 01, 2026 at 05:54:26PM -0700, Brian E. Lavender wrote:
I take it most have heard about the copy fail vulnerability if you have local shell?
https://arstechnica.com/security/2026/04/as-the-most-severe-linux-threat-in-...
I wonder if you patch the hypervisor when using PV guests if you have to update the guests too?
-- Brian Lavender https://www.brie.com/brian/
"There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies."
Professor C. A. R. Hoare The 1980 Turing award lecture _______________________________________________ Lug-nuts mailing list -- lug-nuts@bigbrie.com To unsubscribe send an email to lug-nuts-leave@bigbrie.com
-- -Gary
It is a simple thing to make things complex, a complex thing to make things simple.
Lug-nuts mailing list -- lug-nuts@bigbrie.com To unsubscribe send an email to lug-nuts-leave@bigbrie.com
-- Brian Lavender https://www.brie.com/brian/
"There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies."
Professor C. A. R. Hoare The 1980 Turing award lecture _______________________________________________ Lug-nuts mailing list -- lug-nuts@bigbrie.com To unsubscribe send an email to lug-nuts-leave@bigbrie.com