cbcvebase.
CVE-2024-50220
published 2024-11-09

CVE-2024-50220: In the Linux kernel, the following vulnerability has been resolved: fork: do not invoke uffd on fork if error occurs Patch series "fork: do not expose…

PriorityP415medium4.7CVSS 3.1
AVLACHPRLUINSUCNINAH
EPSS
0.17%
6.4th percentile
In the Linux kernel, the following vulnerability has been resolved: fork: do not invoke uffd on fork if error occurs Patch series "fork: do not expose incomplete mm on fork". During fork we may place the virtual memory address space into an inconsistent state before the fork operation is complete. In addition, we may encounter an error during the fork operation that indicates that the virtual memory address space is invalidated. As a result, we should not be exposing it in any way to external machinery that might interact with the mm or VMAs, machinery that is not designed to deal with incomplete state. We specifically update the fork logic to defer khugepaged and ksm to the end of the operation and only to be invoked if no error arose, and disallow uffd from observing fork events should an error have occurred. This patch (of 2): Currently on fork we expose the virtual address space of a process to userland unconditionally if uffd is registered in VMAs, regardless of whether an error arose in the fork. This is performed in dup_userfaultfd_complete() which is invoked unconditionally, and performs two duties - invoking registered handlers for the UFFD_EVENT_FORK event via dup_fctx(), and clearing down userfaultfd_fork_ctx objects established in dup_userfaultfd(). This is problematic, because the virtual address space may not yet be correctly initialised if an error arose. The change in commit d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") makes this more pertinent as we may be in a state where entries in the maple tree are not yet consistent. We address this by, on fork error, ensuring that we roll back state that we would otherwise expect to clean up through the event being handled by userland and perform the memory freeing duty otherwise performed by dup_userfaultfd_complete(). We do this by implementing a new function, dup_userfaultfd_fail(), which performs the same loop, only decrementing reference counts. Note that we p

Affected

10 ranges
VendorProductVersion rangeFixed in
debianlinux< linux 6.11.7-1 (forky)linux 6.11.7-1 (forky)
linuxlinux
linuxlinux>= d2406291483775ecddaee929231a39c70c08fda2 < 92b472945dbf8abc020e9259c0088026f7027dfc92b472945dbf8abc020e9259c0088026f7027dfc
linuxlinux>= d2406291483775ecddaee929231a39c70c08fda2 < f64e67e5d3a45a4a04286c47afade4b518acd47bf64e67e5d3a45a4a04286c47afade4b518acd47b
linuxlinux_kernel
linuxlinux_kernel>= 0 < 6.11.7-16.11.7-1
linuxlinux_kernel>= 0 < 6.11.7-16.11.7-1
linuxlinux_kernel>= 0 < 6.8.0-58.606.8.0-58.60
linuxlinux_kernel>= 0 < 6.11.0-18.186.11.0-18.18
linuxlinux_kernel>= 6.8 < 6.11.76.11.7

CVSS provenance

nvdv3.14.7MEDIUMCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
osv8.8HIGH
vendor_ubuntu8.8HIGH
vendor_debian4.7LOW
vendor_redhat4.7MEDIUM
Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.