FAILED: patch "[PATCH] mm: take into account mm_cid size for mm_struct static" failed to apply to 6.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x be31340a4cc259340044b7fc4f7e97f58c74ee8e
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026012616-countable-embargo-bbcb@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From be31340a4cc259340044b7fc4f7e97f58c74ee8e Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 24 Dec 2025 12:33:58 -0500
Subject: [PATCH] mm: take into account mm_cid size for mm_struct static
 definitions
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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.

Add a space between # and define for the mm_alloc_cid() definition to make
it consistent with the coding style used in the rest of this header file.

Link: https://lkml.kernel.org/r/20251224173358.647691-4-mathieu.desnoyers@efficios.com
Fixes: af7f588d8f73 ("sched: Introduce per-memory-map concurrency ID")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Thomas Gleixner <tglx@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Aboorva Devarajan <aboorvad@linux.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Christan König <christian.koenig@amd.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Liam R . Howlett" <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Martin Liu <liumartin@google.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 110b319a2ffb..aa4639888f89 100644
--- a/include/linux/mm_types.h
+++ b/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(struct mm_struct *mm, struct task_struct *
 	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(void)
 	return cpumask_size() + bitmap_size(num_possible_cpus());
 }
 
+/* Use 2 * 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(void)
 {
 	return 0;
 }
+# define MM_CID_STATIC_SIZE	0
 #endif /* CONFIG_SCHED_MM_CID */
 
 struct mmu_gather;