Below error was reported in a 32-bit kernel build:
static_call.c:(.ref.text+0x46): undefined reference to `cpu_wants_rethunk_at'
make[1]: [Makefile:1234: vmlinux] Error
This is because the definition of cpu_wants_rethunk_at() depends on
CONFIG_STACK_VALIDATION which is only enabled in 64-bit mode.
Define the empty function for CONFIG_STACK_VALIDATION=n, rethunk mitigation
is anyways not supported without it.
Reported-by: Guenter Roeck <linux(a)roeck-us.net>
Fixes: 5d19a0574b75 ("x86/its: Add support for ITS-safe return thunk")
Signed-off-by: Pawan Gupta <pawan.kumar.gupta(a)linux.intel.com>
Link: https://lore.kernel.org/stable/0f597436-5da6-4319-b918-9f57bde5634a@roeck-u…
---
arch/x86/include/asm/alternative.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 1797f80c10de..a5f704dbb4a1 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -98,7 +98,7 @@ static inline u8 *its_static_thunk(int reg)
}
#endif
-#ifdef CONFIG_RETHUNK
+#if defined(CONFIG_RETHUNK) && defined(CONFIG_STACK_VALIDATION)
extern bool cpu_wants_rethunk(void);
extern bool cpu_wants_rethunk_at(void *addr);
#else
--
2.34.1
The quilt patch titled
Subject: mm/khugepaged: fix race with folio split/free using temporary reference
has been removed from the -mm tree. Its filename was
mm-khugepaged-fix-race-with-folio-split-free-using-temporary-reference.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Shivank Garg <shivankg(a)amd.com>
Subject: mm/khugepaged: fix race with folio split/free using temporary reference
Date: Mon, 26 May 2025 18:28:18 +0000
hpage_collapse_scan_file() calls is_refcount_suitable(), which in turn
calls folio_mapcount(). folio_mapcount() checks folio_test_large() before
proceeding to folio_large_mapcount(), but there is a race window where the
folio may get split/freed between these checks, triggering:
VM_WARN_ON_FOLIO(!folio_test_large(folio), folio)
Take a temporary reference to the folio in hpage_collapse_scan_file().
This stabilizes the folio during refcount check and prevents incorrect
large folio detection due to concurrent split/free. Use helper
folio_expected_ref_count() + 1 to compare with folio_ref_count() instead
of using is_refcount_suitable().
Link: https://lkml.kernel.org/r/20250526182818.37978-1-shivankg@amd.com
Fixes: 05c5323b2a34 ("mm: track mapcount of large folios in single value")
Signed-off-by: Shivank Garg <shivankg(a)amd.com>
Reported-by: syzbot+2b99589e33edbe9475ca(a)syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/6828470d.a70a0220.38f255.000c.GAE@google.com
Suggested-by: David Hildenbrand <david(a)redhat.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Acked-by: Dev Jain <dev.jain(a)arm.com>
Reviewed-by: Baolin Wang <baolin.wang(a)linux.alibaba.com>
Cc: Bharata B Rao <bharata(a)amd.com>
Cc: Fengwei Yin <fengwei.yin(a)intel.com>
Cc: Liam Howlett <liam.howlett(a)oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com>
Cc: Mariano Pache <npache(a)redhat.com>
Cc: Ryan Roberts <ryan.roberts(a)arm.com>
Cc: Zi Yan <ziy(a)nvidia.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/khugepaged.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
--- a/mm/khugepaged.c~mm-khugepaged-fix-race-with-folio-split-free-using-temporary-reference
+++ a/mm/khugepaged.c
@@ -2293,6 +2293,17 @@ static int hpage_collapse_scan_file(stru
continue;
}
+ if (!folio_try_get(folio)) {
+ xas_reset(&xas);
+ continue;
+ }
+
+ if (unlikely(folio != xas_reload(&xas))) {
+ folio_put(folio);
+ xas_reset(&xas);
+ continue;
+ }
+
if (folio_order(folio) == HPAGE_PMD_ORDER &&
folio->index == start) {
/* Maybe PMD-mapped */
@@ -2303,23 +2314,27 @@ static int hpage_collapse_scan_file(stru
* it's safe to skip LRU and refcount checks before
* returning.
*/
+ folio_put(folio);
break;
}
node = folio_nid(folio);
if (hpage_collapse_scan_abort(node, cc)) {
result = SCAN_SCAN_ABORT;
+ folio_put(folio);
break;
}
cc->node_load[node]++;
if (!folio_test_lru(folio)) {
result = SCAN_PAGE_LRU;
+ folio_put(folio);
break;
}
- if (!is_refcount_suitable(folio)) {
+ if (folio_expected_ref_count(folio) + 1 != folio_ref_count(folio)) {
result = SCAN_PAGE_COUNT;
+ folio_put(folio);
break;
}
@@ -2331,6 +2346,7 @@ static int hpage_collapse_scan_file(stru
*/
present += folio_nr_pages(folio);
+ folio_put(folio);
if (need_resched()) {
xas_pause(&xas);
_
Patches currently in -mm which might be from shivankg(a)amd.com are