+ mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug.patch added to mm-unstable branch

+ mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/vmalloc: add a safer version of find_vm_area() for debug
has been added to the -mm mm-unstable branch.  Its filename is
     mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug.patch

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

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------------------------------------------------------
From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Subject: mm/vmalloc: add a safer version of find_vm_area() for debug
Date: Wed, 30 Aug 2023 11:03:59 +0000

It is unsafe to dump vmalloc area information when trying to do so from
some contexts.  Add a safer trylock version of the same function to do a
best-effort VMA finding and use it from vmalloc_dump_obj().

Link: https://lkml.kernel.org/r/20230830110402.386898-1-joel@joelfernandes.org
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reported-by: Zhen Lei <thunder.leizhen@huaweicloud.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Zqiang <qiang.zhang1211@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmalloc.c |   35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

--- a/mm/vmalloc.c~mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug
+++ a/mm/vmalloc.c
@@ -1865,6 +1865,18 @@ struct vmap_area *find_vmap_area(unsigne
 	return va;
 }
 
+static struct vmap_area *find_vmap_area_trylock(unsigned long addr)
+{
+	struct vmap_area *va;
+
+	if (!spin_trylock(&vmap_area_lock))
+		return NULL;
+	va = __find_vmap_area(addr, &vmap_area_root);
+	spin_unlock(&vmap_area_lock);
+
+	return va;
+}
+
 static struct vmap_area *find_unlink_vmap_area(unsigned long addr)
 {
 	struct vmap_area *va;
@@ -2672,6 +2684,27 @@ struct vm_struct *find_vm_area(const voi
 }
 
 /**
+ * try_to_find_vm_area - find a continuous kernel virtual area
+ * @addr:	  base address
+ *
+ * This function is the same as find_vm_area() except that it is
+ * safe to call if vmap_area_lock is already held and returns NULL
+ * if it is. See comments in find_vmap_area() for other details.
+ *
+ * Return: the area descriptor on success or %NULL on failure.
+ */
+static struct vm_struct *try_to_find_vm_area(const void *addr)
+{
+	struct vmap_area *va;
+
+	va = find_vmap_area_trylock((unsigned long)addr);
+	if (!va)
+		return NULL;
+
+	return va->vm;
+}
+
+/**
  * remove_vm_area - find and remove a continuous kernel virtual area
  * @addr:	    base address
  *
@@ -4281,7 +4314,7 @@ bool vmalloc_dump_obj(void *object)
 	struct vm_struct *vm;
 	void *objp = (void *)PAGE_ALIGN((unsigned long)object);
 
-	vm = find_vm_area(objp);
+	vm = try_to_find_vm_area(objp);
 	if (!vm)
 		return false;
 	pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n",
_

Patches currently in -mm which might be from joel@joelfernandes.org are

mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug.patch