mirror of
https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9.git
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Vitaly Kuznetsov
1b122192e0
JIRA: https://redhat.atlassian.net/browse/RHEL-172489
CVE: CVE-2026-31787
commit 24daca4fc07f3ff8cd0e3f629cd982187f48436a
Author: Juergen Gross <jgross@suse.com>
Date: Fri Apr 10 09:20:04 2026 +0200
xen/privcmd: fix double free via VMA splitting
privcmd_vm_ops defines .close (privcmd_close), but neither .may_split
nor .open. When userspace does a partial munmap() on a privcmd mapping,
the kernel splits the VMA via __split_vma(). Since may_split is NULL,
the split is allowed. vm_area_dup() copies vm_private_data (a pages
array allocated in alloc_empty_pages()) into the new VMA without any
fixup, because there is no .open callback.
Both VMAs now point to the same pages array. When the unmapped portion
is closed, privcmd_close() calls:
- xen_unmap_domain_gfn_range()
- xen_free_unpopulated_pages()
- kvfree(pages)
The surviving VMA still holds the dangling pointer. When it is later
destroyed, the same sequence runs again, which leads to a double free.
Fix this issue by adding a .may_split callback denying the VMA split.
This is XSA-487 / CVE-2026-31787
Fixes: d71f513985 ("xen: privcmd: support autotranslated physmap guests.")
Reported-by: Atharva Vartak <atharva.a.vartak@gmail.com>
Suggested-by: Atharva Vartak <atharva.a.vartak@gmail.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.