FAILED: patch "[PATCH] mm/cma_debug: fix invalid accesses for inactive CMA areas" failed to apply to 6.6-stable tree

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 <[email protected]>.

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 c0ca59beb5252ea2bd4fdaef009d003dedc2030e
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026061503-igloo-gainfully-c809@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From c0ca59beb5252ea2bd4fdaef009d003dedc2030e Mon Sep 17 00:00:00 2001
From: Muchun Song <[email protected]>
Date: Wed, 20 May 2026 14:10:25 +0800
Subject: [PATCH] mm/cma_debug: fix invalid accesses for inactive CMA areas

cma_activate_area() can fail after allocating range bitmaps. Its cleanup path frees those bitmaps, but only clears cma->count and cma->available_count. It leaves cma->nranges and each range's count in place, so cma_debugfs_init() can still register debugfs files for an area that never activated successfully.

That exposes two problems. Reading the bitmap file can make debugfs walk a freed range bitmap and trigger an invalid memory access. Reading maxchunk can also take cma->lock even though that lock is initialized only on the successful activation path.

Fix this by creating debugfs entries only for CMA areas that reached CMA_ACTIVATED.

c009da4258f9 introduced the invalid access to bitmap file. 2e32b947606d introduced the invalid access to cma->lock. This change applies to both issues. So I added two Fixes tags.

index 5ae38f5abbcc..523ba4a0f9f7 100644
@@ -205,7 +205,8 @@ static int __init cma_debugfs_init(void)
 	cma_debugfs_root = debugfs_create_dir("cma", NULL);
 
 	for (i = 0; i < cma_area_count; i++)
-		cma_debugfs_add_one(&cma_areas[i], cma_debugfs_root);
+		if (test_bit(CMA_ACTIVATED, &cma_areas[i].flags))
+			cma_debugfs_add_one(&cma_areas[i], cma_debugfs_root);
 
 	return 0;
 }