+ mm-take-into-account-mm_cid-size-for-mm_struct-static-definitions.patch added to mm-new branch

+ mm-take-into-account-mm_cid-size-for-mm_struct-static-definitions.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm: take into account mm_cid size for mm_struct static definitions
has been added to the -mm mm-new branch.  Its filename is
     mm-take-into-account-mm_cid-size-for-mm_struct-static-definitions.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-take-into-account-mm_cid-size-for-mm_struct-static-definitions.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

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------------------------------------------------------
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: mm: take into account mm_cid size for mm_struct static definitions
Date: Sun, 21 Dec 2025 18:29:24 -0500

Both init_mm and efi_mm static definitions need to make room for the
2 mm_cid cpumasks.

This fixes possible out-of-bounds accesses to init_mm and efi_mm.

Link: https://lkml.kernel.org/r/20251221232926.450602-4-mathieu.desnoyers@efficios.com
Fixes: af7f588d8f73 ("sched: Introduce per-memory-map concurrency ID")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mark Brown <broonie@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm_types.h |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/include/linux/mm_types.h~mm-take-into-account-mm_cid-size-for-mm_struct-static-definitions
+++ a/include/linux/mm_types.h
@@ -1368,7 +1368,7 @@ extern struct mm_struct init_mm;
 
 #define MM_STRUCT_FLEXIBLE_ARRAY_INIT				\
 {								\
-	[0 ... sizeof(cpumask_t)-1] = 0				\
+	[0 ... sizeof(cpumask_t) + MM_CID_STATIC_SIZE - 1] = 0	\
 }
 
 /* Pointer magic because the dynamic array size confuses some compilers. */
@@ -1500,7 +1500,7 @@ static inline int mm_alloc_cid_noprof(st
 	mm_init_cid(mm, p);
 	return 0;
 }
-#define mm_alloc_cid(...)	alloc_hooks(mm_alloc_cid_noprof(__VA_ARGS__))
+# define mm_alloc_cid(...)	alloc_hooks(mm_alloc_cid_noprof(__VA_ARGS__))
 
 static inline void mm_destroy_cid(struct mm_struct *mm)
 {
@@ -1514,6 +1514,8 @@ static inline unsigned int mm_cid_size(v
 	return cpumask_size() + bitmap_size(num_possible_cpus());
 }
 
+/* Use NR_CPUS as worse case for static allocation. */
+# define MM_CID_STATIC_SIZE	(2 * sizeof(cpumask_t))
 #else /* CONFIG_SCHED_MM_CID */
 static inline void mm_init_cid(struct mm_struct *mm, struct task_struct *p) { }
 static inline int mm_alloc_cid(struct mm_struct *mm, struct task_struct *p) { return 0; }
@@ -1522,6 +1524,7 @@ static inline unsigned int mm_cid_size(v
 {
 	return 0;
 }
+# define MM_CID_STATIC_SIZE	0
 #endif /* CONFIG_SCHED_MM_CID */
 
 struct mmu_gather;
_

Patches currently in -mm which might be from mathieu.desnoyers@efficios.com are

lib-introduce-hierarchical-per-cpu-counters.patch
mm-fix-oom-killer-inaccuracy-on-large-many-core-systems.patch
mm-implement-precise-oom-killer-task-selection.patch
mm-add-missing-static-initializer-for-init_mm-mm_cidlock.patch
mm-rename-cpu_bitmap-field-to-flexible_array.patch
mm-take-into-account-mm_cid-size-for-mm_struct-static-definitions.patch
mm-take-into-account-hierarchical-percpu-tree-items-for-static-mm_struct-definitions.patch
tsacct-skip-all-kernel-threads.patch