From: Juergen Gross <jgross@suse.com> mainline inclusion from mainline-v7.0-rc6 commit 1613462be621ad5103ec338a7b0ca0746ec4e5f1 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14027 CVE: CVE-2026-31788 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- When running in an unprivileged domU under Xen, the privcmd driver is restricted to allow only hypercalls against a target domain, for which the current domU is acting as a device model. Add a boot parameter "unrestricted" to allow all hypercalls (the hypervisor will still refuse destructive hypercalls affecting other guests). Make this new parameter effective only in case the domU wasn't started using secure boot, as otherwise hypercalls targeting the domU itself might result in violating the secure boot functionality. This is achieved by adding another lockdown reason, which can be tested to not being set when applying the "unrestricted" option. This is part of XSA-482 Signed-off-by: Juergen Gross <jgross@suse.com> Conflicts: drivers/xen/privcmd.c [commit f0d7db7b33243 not merged] Signed-off-by: Zhang Yuwei <zhangyuwei20@huawei.com> --- drivers/xen/privcmd.c | 13 +++++++++++++ include/linux/security.h | 1 + security/security.c | 1 + 3 files changed, 15 insertions(+) diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index 29bb4ea7af9b..74d6a2bd6d04 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -32,6 +32,7 @@ #include <linux/miscdevice.h> #include <linux/moduleparam.h> #include <linux/notifier.h> +#include <linux/security.h> #include <linux/wait.h> #include <asm/xen/hypervisor.h> #include <asm/xen/hypercall.h> @@ -63,6 +64,11 @@ module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint, MODULE_PARM_DESC(dm_op_buf_max_size, "Maximum size of a dm_op hypercall buffer"); +static bool unrestricted; +module_param(unrestricted, bool, 0); +MODULE_PARM_DESC(unrestricted, + "Don't restrict hypercalls to target domain if running in a domU"); + struct privcmd_data { domid_t domid; }; @@ -1299,6 +1305,13 @@ static struct notifier_block xenstore_notifier = { static void __init restrict_driver(void) { + if (unrestricted) { + if (security_locked_down(LOCKDOWN_XEN_USER_ACTIONS)) + pr_warn("Kernel is locked down, parameter \"unrestricted\" ignored\n"); + else + return; + } + restrict_wait = true; register_xenstore_notifier(&xenstore_notifier); diff --git a/include/linux/security.h b/include/linux/security.h index 4bd0f6fc553e..937840870d86 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -125,6 +125,7 @@ enum lockdown_reason { LOCKDOWN_BPF_WRITE_USER, LOCKDOWN_DBG_WRITE_KERNEL, LOCKDOWN_RTAS_ERROR_INJECTION, + LOCKDOWN_XEN_USER_ACTIONS, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_KCORE, LOCKDOWN_KPROBES, diff --git a/security/security.c b/security/security.c index 839e12addac7..66edcbcd1a97 100644 --- a/security/security.c +++ b/security/security.c @@ -61,6 +61,7 @@ const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX + 1] = { [LOCKDOWN_BPF_WRITE_USER] = "use of bpf to write user RAM", [LOCKDOWN_DBG_WRITE_KERNEL] = "use of kgdb/kdb to write kernel RAM", [LOCKDOWN_RTAS_ERROR_INJECTION] = "RTAS error injection", + [LOCKDOWN_XEN_USER_ACTIONS] = "Xen guest user action", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_KCORE] = "/proc/kcore access", [LOCKDOWN_KPROBES] = "use of kprobes", -- 2.22.0