The patch titled Subject: maple_tree: fix MA_STATE_PREALLOC flag in mas_preallocate() has been added to the -mm mm-hotfixes-unstable branch. Its filename is maple_tree-fix-ma_state_prealloc-flag-in-mas_preallocate.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

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

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------------------------------------------------------ From: "Liam R. Howlett" Liam.Howlett@oracle.com Subject: maple_tree: fix MA_STATE_PREALLOC flag in mas_preallocate() Date: Mon, 16 Jun 2025 14:45:20 -0400

Temporarily clear the preallocation flag when explicitly requesting allocations. Pre-existing allocations are already counted against the request through mas_node_count_gfp(), but the allocations will not happen if the MA_STATE_PREALLOC flag is set. This flag is meant to avoid re-allocating in bulk allocation mode, and to detect issues with preallocation calculations.

The MA_STATE_PREALLOC flag should also always be set on zero allocations so that detection of underflow allocations will print a WARN_ON() during consumption.

User visible effect of this flaw is a WARN_ON() followed by a null pointer dereference when subsequent requests for larger number of nodes is ignored, such as the vma merge retry in mmap_region() caused by drivers altering the vma flags (which happens in v6.6, at least)

Link: https://lkml.kernel.org/r/20250616184521.3382795-3-Liam.Howlett@oracle.com Fixes: 54a611b605901 ("Maple Tree: add new data structure") Signed-off-by: Liam R. Howlett Liam.Howlett@oracle.com Reported-by: Zhaoyang Huang zhaoyang.huang@unisoc.com Reported-by: Hailong Liu hailong.liu@oppo.com Link: https://lore.kernel.org/all/1652f7eb-a51b-4fee-8058-c73af63bacd1@oppo.com/ Link: https://lore.kernel.org/all/20250428184058.1416274-1-Liam.Howlett@oracle.com... Link: https://lore.kernel.org/all/20250429014754.1479118-1-Liam.Howlett@oracle.com... Cc: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: Suren Baghdasaryan surenb@google.com Cc: Hailong Liu hailong.liu@oppo.com Cc: zhangpeng.00@bytedance.com zhangpeng.00@bytedance.com Cc: Steve Kang Steve.Kang@unisoc.com Cc: Matthew Wilcox willy@infradead.org Cc: Sidhartha Kumar sidhartha.kumar@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

lib/maple_tree.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/lib/maple_tree.c~maple_tree-fix-ma_state_prealloc-flag-in-mas_preallocate +++ a/lib/maple_tree.c @@ -5527,8 +5527,9 @@ int mas_preallocate(struct ma_state *mas mas->store_type = mas_wr_store_type(&wr_mas); request = mas_prealloc_calc(&wr_mas, entry); if (!request) - return ret; + goto set_flag;

+ mas->mas_flags &= ~MA_STATE_PREALLOC; mas_node_count_gfp(mas, request, gfp); if (mas_is_err(mas)) { mas_set_alloc_req(mas, 0); @@ -5538,6 +5539,7 @@ int mas_preallocate(struct ma_state *mas return ret; }

+set_flag: mas->mas_flags |= MA_STATE_PREALLOC; return ret; } _

Patches currently in -mm which might be from Liam.Howlett@oracle.com are

maple_tree-fix-ma_state_prealloc-flag-in-mas_preallocate.patch testing-raix-tree-maple-increase-readers-and-reduce-delay-for-faster-machines.patch