x86/sgx: Do not fail on incomplete sanitization on premature stop of ksgxd

BugLink: https://bugs.launchpad.net/bugs/1995517
commit 133e049a3f8c91b175029fb6a59b6039d5e79cba upstream.

Unsanitized pages trigger WARN_ON() unconditionally, which can panic the
whole computer, if /proc/sys/kernel/panic_on_warn is set.

In sgx_init(), if misc_register() fails or misc_register() succeeds but
neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be
prematurely stopped. This may leave unsanitized pages, which will result a
false warning.

Refine __sgx_sanitize_pages() to return:

1. Zero when the sanitization process is complete or ksgxd has been
   requested to stop.
2. The number of unsanitized pages otherwise.

Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list")
Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/linux-sgx/20220825051827.246698-1-jarkko@kernel.org/T/#u
Link: https://lkml.kernel.org/r/20220906000221.34286-2-jarkko@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index c93c9f9f8c7b969c7d7fe5fefbaaee473aefeca9..4ea48acf55faa0970cd79438727ebea7af9a2bed 100644 (file)
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -46,9 +46,13 @@ static LIST_HEAD(sgx_dirty_page_list);
  * Reset post-kexec EPC pages to the uninitialized state. The pages are removed
  * from the input list, and made available for the page allocator. SECS pages
  * prepending their children in the input list are left intact.
+ *
+ * Return 0 when sanitization was successful or kthread was stopped, and the
+ * number of unsanitized pages otherwise.
  */
-static void __sgx_sanitize_pages(struct list_head *dirty_page_list)
+static unsigned long __sgx_sanitize_pages(struct list_head *dirty_page_list)
 {
+       unsigned long left_dirty = 0;
        struct sgx_epc_page *page;
        LIST_HEAD(dirty);
        int ret;
@@ -56,7 +60,7 @@ static void __sgx_sanitize_pages(struct list_head *dirty_page_list)
        /* dirty_page_list is thread-local, no need for a lock: */
        while (!list_empty(dirty_page_list)) {
                if (kthread_should_stop())
-                       return;
+                       return 0;
 
                page = list_first_entry(dirty_page_list, struct sgx_epc_page, list);
 
@@ -71,12 +75,14 @@ static void __sgx_sanitize_pages(struct list_head *dirty_page_list)
                } else {
                        /* The page is not yet clean - move to the dirty list. */
                        list_move_tail(&page->list, &dirty);
+                       left_dirty++;
                }
 
                cond_resched();
        }
 
        list_splice(&dirty, dirty_page_list);
+       return left_dirty;
 }
 
 static bool sgx_reclaimer_age(struct sgx_epc_page *epc_page)
@@ -427,10 +433,7 @@ static int ksgxd(void *p)
         * required for SECS pages, whose child pages blocked EREMOVE.
         */
        __sgx_sanitize_pages(&sgx_dirty_page_list);
-       __sgx_sanitize_pages(&sgx_dirty_page_list);
-
-       /* sanity check: */
-       WARN_ON(!list_empty(&sgx_dirty_page_list));
+       WARN_ON(__sgx_sanitize_pages(&sgx_dirty_page_list));
 
        while (!kthread_should_stop()) {
                if (try_to_freeze())