+ mm-kmsan-fix-kmsan-kmalloc-hook-when-no-stack-depots-are-allocated-yet.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/kmsan: Fix kmsan kmalloc hook when no stack depots are allocated yet
has been added to the -mm mm-new branch.  Its filename is
     mm-kmsan-fix-kmsan-kmalloc-hook-when-no-stack-depots-are-allocated-yet.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-kmsan-fix-kmsan-kmalloc-hook-when-no-stack-depots-are-allocated-yet.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: Aleksei Nikiforov <aleksei.nikiforov@linux.ibm.com>
Subject: mm/kmsan: Fix kmsan kmalloc hook when no stack depots are allocated yet
Date: Tue, 30 Sep 2025 13:56:01 +0200

If no stack depot is allocated yet, due to masking out __GFP_RECLAIM flags
kmsan called from kmalloc cannot allocate stack depot.  kmsan fails to
record origin and report issues.

Reusing flags from kmalloc without modifying them should be safe for kmsan.
For example, such chain of calls is possible:
test_uninit_kmalloc -> kmalloc -> __kmalloc_cache_noprof ->
slab_alloc_node -> slab_post_alloc_hook ->
kmsan_slab_alloc -> kmsan_internal_poison_memory.

Only when it is called in a context without flags present should
__GFP_RECLAIM flags be masked.

With this change all kmsan tests start working reliably.

Link: https://lkml.kernel.org/r/20250930115600.709776-2-aleksei.nikiforov@linux.ibm.com
Signed-off-by: Aleksei Nikiforov <aleksei.nikiforov@linux.ibm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kmsan/core.c   |    3 ---
 mm/kmsan/hooks.c  |    6 ++++--
 mm/kmsan/shadow.c |    2 +-
 3 files changed, 5 insertions(+), 6 deletions(-)

--- a/mm/kmsan/core.c~mm-kmsan-fix-kmsan-kmalloc-hook-when-no-stack-depots-are-allocated-yet
+++ a/mm/kmsan/core.c
@@ -72,9 +72,6 @@ depot_stack_handle_t kmsan_save_stack_wi
 
 	nr_entries = stack_trace_save(entries, KMSAN_STACK_DEPTH, 0);
 
-	/* Don't sleep. */
-	flags &= ~(__GFP_DIRECT_RECLAIM | __GFP_KSWAPD_RECLAIM);
-
 	handle = stack_depot_save(entries, nr_entries, flags);
 	return stack_depot_set_extra_bits(handle, extra);
 }
--- a/mm/kmsan/hooks.c~mm-kmsan-fix-kmsan-kmalloc-hook-when-no-stack-depots-are-allocated-yet
+++ a/mm/kmsan/hooks.c
@@ -84,7 +84,8 @@ void kmsan_slab_free(struct kmem_cache *
 	if (s->ctor)
 		return;
 	kmsan_enter_runtime();
-	kmsan_internal_poison_memory(object, s->object_size, GFP_KERNEL,
+	kmsan_internal_poison_memory(object, s->object_size,
+				     GFP_KERNEL & ~(__GFP_RECLAIM),
 				     KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
 	kmsan_leave_runtime();
 }
@@ -114,7 +115,8 @@ void kmsan_kfree_large(const void *ptr)
 	kmsan_enter_runtime();
 	page = virt_to_head_page((void *)ptr);
 	KMSAN_WARN_ON(ptr != page_address(page));
-	kmsan_internal_poison_memory((void *)ptr, page_size(page), GFP_KERNEL,
+	kmsan_internal_poison_memory((void *)ptr, page_size(page),
+				     GFP_KERNEL & ~(__GFP_RECLAIM),
 				     KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
 	kmsan_leave_runtime();
 }
--- a/mm/kmsan/shadow.c~mm-kmsan-fix-kmsan-kmalloc-hook-when-no-stack-depots-are-allocated-yet
+++ a/mm/kmsan/shadow.c
@@ -208,7 +208,7 @@ void kmsan_free_page(struct page *page,
 		return;
 	kmsan_enter_runtime();
 	kmsan_internal_poison_memory(page_address(page), page_size(page),
-				     GFP_KERNEL,
+				     GFP_KERNEL & ~(__GFP_RECLAIM),
 				     KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
 	kmsan_leave_runtime();
 }
_

Patches currently in -mm which might be from aleksei.nikiforov@linux.ibm.com are

mm-kmsan-fix-kmsan-kmalloc-hook-when-no-stack-depots-are-allocated-yet.patch