The patch below does not apply to the 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x fba46a5d83ca8decb338722fb4899026d8d9ead2 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025063032-shed-reseller-6709@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From fba46a5d83ca8decb338722fb4899026d8d9ead2 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Liam.Howlett@oracle.com Date: Mon, 16 Jun 2025 14:45:20 -0400 Subject: [PATCH] maple_tree: fix MA_STATE_PREALLOC flag in mas_preallocate()

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: 54a611b60590 ("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

diff --git a/lib/maple_tree.c b/lib/maple_tree.c index affe979bd14d..00524e55a21e 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -5527,8 +5527,9 @@ int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp) 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, void *entry, gfp_t gfp) return ret; }

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