CVE-2026-74606: eventfs: Fix use-after-free in eventfs_remove_rec()

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

eventfs: Fix use-after-free in eventfs_remove_rec()

eventfs_remove_rec() recursively removes the child at the current loop
position. After the recursive call returns, list_for_each_entry() advances
by reading list.next from the removed child.

If free_ei() drops the final reference, release_ei() reuses the list/rcu
union to queue an SRCU callback. The child may be freed before that read.
The eventfs_mutex serializes list updates, but it does not keep the removed
child alive or prevent the SRCU callback from running.

Use list_for_each_entry_safe() to save the next sibling before recursively
removing the current child.

The Linux kernel CVE team has assigned CVE-2026-74606 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.6.18 with commit 5dfb04100326f70e3b2d2872c2476ed20b804837 and fixed in 6.6.152 with commit b77581b25e213e83b79ce11eb30024e55ceeb3e9
	Issue introduced in 6.8 with commit 43aa6f97c2d03a52c1ddb86768575fc84344bdbb and fixed in 6.12.104 with commit f161d7861a0bfdf10af6b738b3b57636204661fb
	Issue introduced in 6.8 with commit 43aa6f97c2d03a52c1ddb86768575fc84344bdbb and fixed in 6.18.45 with commit 5635211b44969f4816e29ec4d5f8665fb39535d0
	Issue introduced in 6.8 with commit 43aa6f97c2d03a52c1ddb86768575fc84344bdbb and fixed in 7.1.9 with commit 74bb1eaf72d185a78c879eb2678ea500f82f46a8
	Issue introduced in 6.8 with commit 43aa6f97c2d03a52c1ddb86768575fc84344bdbb and fixed in 7.2 with commit fd73b691702170d37d66f4b0278530cea8ed419a
	Issue introduced in 6.7.6 with commit 5a43badefe0eccca0c26144c0a44b8d417ce8103

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-74606
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/tracefs/event_inode.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/b77581b25e213e83b79ce11eb30024e55ceeb3e9
	https://git.kernel.org/stable/c/f161d7861a0bfdf10af6b738b3b57636204661fb
	https://git.kernel.org/stable/c/5635211b44969f4816e29ec4d5f8665fb39535d0
	https://git.kernel.org/stable/c/74bb1eaf72d185a78c879eb2678ea500f82f46a8
	https://git.kernel.org/stable/c/fd73b691702170d37d66f4b0278530cea8ed419a