From: Weiming Shi <bestswngs@gmail.com> stable inclusion from stable-v6.6.131 commit 9c886e63b69658959633937e3acb7ca8addf7499 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14159 CVE: CVE-2026-31426 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- When ec_install_handlers() returns -EPROBE_DEFER on reduced-hardware platforms, it has already started the EC and installed the address space handler with the struct acpi_ec pointer as handler context. However, acpi_ec_setup() propagates the error without any cleanup. The caller acpi_ec_add() then frees the struct acpi_ec for non-boot instances, leaving a dangling handler context in ACPICA. Any subsequent AML evaluation that accesses an EC OpRegion field dispatches into acpi_ec_space_handler() with the freed pointer, causing a use-after-free: BUG: KASAN: slab-use-after-free in mutex_lock (kernel/locking/mutex.c:289) Write of size 8 at addr ffff88800721de38 by task init/1 Call Trace: <TASK> mutex_lock (kernel/locking/mutex.c:289) acpi_ec_space_handler (drivers/acpi/ec.c:1362) acpi_ev_address_space_dispatch (drivers/acpi/acpica/evregion.c:293) acpi_ex_access_region (drivers/acpi/acpica/exfldio.c:246) acpi_ex_field_datum_io (drivers/acpi/acpica/exfldio.c:509) acpi_ex_extract_from_field (drivers/acpi/acpica/exfldio.c:700) acpi_ex_read_data_from_field (drivers/acpi/acpica/exfield.c:327) acpi_ex_resolve_node_to_value (drivers/acpi/acpica/exresolv.c:392) </TASK> Allocated by task 1: acpi_ec_alloc (drivers/acpi/ec.c:1424) acpi_ec_add (drivers/acpi/ec.c:1692) Freed by task 1: kfree (mm/slub.c:6876) acpi_ec_add (drivers/acpi/ec.c:1751) The bug triggers on reduced-hardware EC platforms (ec->gpe < 0) when the GPIO IRQ provider defers probing. Once the stale handler exists, any unprivileged sysfs read that causes AML to touch an EC OpRegion (battery, thermal, backlight) exercises the dangling pointer. Fix this by calling ec_remove_handlers() in the error path of acpi_ec_setup() before clearing first_ec. ec_remove_handlers() checks each EC_FLAGS_* bit before acting, so it is safe to call regardless of how far ec_install_handlers() progressed: -ENODEV (handler not installed): only calls acpi_ec_stop() -EPROBE_DEFER (handler installed): removes handler, stops EC Fixes: 03e9a0e05739 ("ACPI: EC: Consolidate event handler installation code") Reported-by: Xiang Mei <xmei5@asu.edu> Signed-off-by: Weiming Shi <bestswngs@gmail.com> Link: https://patch.msgid.link/20260324165458.1337233-2-bestswngs@gmail.com Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Conflicts: drivers/acpi/ec.c [context conflict] Signed-off-by: Xinyu Zheng <zhengxinyu6@huawei.com> --- drivers/acpi/ec.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c index b20206316fbe..79b4dd9b733b 100644 --- a/drivers/acpi/ec.c +++ b/drivers/acpi/ec.c @@ -1618,8 +1618,10 @@ static int acpi_ec_setup(struct acpi_ec *ec, struct acpi_device *device) int ret; ret = ec_install_handlers(ec, device); - if (ret) + if (ret) { + ec_remove_handlers(ec); return ret; + } /* First EC capable of handling transactions */ if (!first_ec) -- 2.34.1