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FAILED: patch "[PATCH] mm/mmap: Fix error path in do_vmi_align_munmap()" failed to apply to 6.3-stable tree

PATCH [email protected] 1 participant 1 message Jun 19, 2023

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The patch below does not apply to the 6.3-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-6.3.y
git checkout FETCH_HEAD
git cherry-pick -x 606c812eb1d5b5fb0dd9e330ca94b52d7c227830
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023061957-faceplate-coeditor-ef11@gregkh' --subject-prefix 'PATCH 6.3.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 606c812eb1d5b5fb0dd9e330ca94b52d7c227830 Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" <[email protected]>
Date: Sat, 17 Jun 2023 20:47:08 -0400
Subject: [PATCH] mm/mmap: Fix error path in do_vmi_align_munmap()

The error unrolling was leaving the VMAs detached in many cases and leaving the locked_vm statistic altered, and skipping the unrolling entirely in the case of the vma tree write failing.

Fix the error path by re-attaching the detached VMAs and adding the necessary goto for the failed vma tree write, and fix the locked_vm statistic by only updating after the vma tree write succeeds.

Fixes 763ecb035029 ("mm: remove the vma linked list")
Reported-by Vegard Nossum <[email protected]>
Signed-off-by Liam R. Howlett <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
mm/mmap.c +17 -20
index 13678edaa22c..d600404580b2 100644
@@ -2318,21 +2318,6 @@ int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	return __split_vma(vmi, vma, addr, new_below);
 }
 
-static inline int munmap_sidetree(struct vm_area_struct *vma,
-				   struct ma_state *mas_detach)
-{
-	vma_start_write(vma);
-	mas_set_range(mas_detach, vma->vm_start, vma->vm_end - 1);
-	if (mas_store_gfp(mas_detach, vma, GFP_KERNEL))
-		return -ENOMEM;
-
-	vma_mark_detached(vma, true);
-	if (vma->vm_flags & VM_LOCKED)
-		vma->vm_mm->locked_vm -= vma_pages(vma);
-
-	return 0;
-}
-
 /*
  * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
  * @vmi: The vma iterator

@@ -2354,6 +2339,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	struct maple_tree mt_detach;
 	int count = 0;
 	int error = -ENOMEM;
+	unsigned long locked_vm = 0;
 	MA_STATE(mas_detach, &mt_detach, 0, 0);
 	mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
 	mt_set_external_lock(&mt_detach, &mm->mmap_lock);

@@ -2399,9 +2385,13 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 			if (error)
 				goto end_split_failed;
 		}
-		error = munmap_sidetree(next, &mas_detach);
-		if (error)
-			goto munmap_sidetree_failed;
+		vma_start_write(next);
+		mas_set_range(&mas_detach, next->vm_start, next->vm_end - 1);
+		if (mas_store_gfp(&mas_detach, next, GFP_KERNEL))
+			goto munmap_gather_failed;
+		vma_mark_detached(next, true);
+		if (next->vm_flags & VM_LOCKED)
+			locked_vm += vma_pages(next);
 
 		count++;
 #ifdef CONFIG_DEBUG_VM_MAPLE_TREE

@@ -2447,10 +2437,12 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	}
 #endif
 	/* Point of no return */
+	error = -ENOMEM;
 	vma_iter_set(vmi, start);
 	if (vma_iter_clear_gfp(vmi, start, end, GFP_KERNEL))
-		return -ENOMEM;
+		goto clear_tree_failed;
 
+	mm->locked_vm -= locked_vm;
 	mm->map_count -= count;
 	/*
 	 * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or

@@ -2480,9 +2472,14 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	validate_mm(mm);
 	return downgrade ? 1 : 0;
 
+clear_tree_failed:
 userfaultfd_error:
-munmap_sidetree_failed:
+munmap_gather_failed:
 end_split_failed:
+	mas_set(&mas_detach, 0);
+	mas_for_each(&mas_detach, next, end)
+		vma_mark_detached(next, false);
+
 	__mt_destroy(&mt_detach);
 start_split_failed:
 map_count_exceeded: