From: Joel Fernandes (Google) <joel@joelfernandes.org>
Date: Mon, 4 Sep 2023 18:08:04 +0000 (+0000)
Subject: mm/vmalloc: add a safer version of find_vm_area() for debug
X-Git-Tag: v6.6.17~3986^2~4
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=0818e739b5c061b0251c30152380600fb9b84c0c;p=platform%2Fkernel%2Flinux-rpi.git

mm/vmalloc: add a safer version of find_vm_area() for debug

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().

[applied test robot feedback on unused function fix.]
[applied Uladzislau feedback on locking.]
Link: https://lkml.kernel.org/r/20230904180806.1002832-1-joel@joelfernandes.org
Fixes: 98f180837a89 ("mm: Make mem_dump_obj() handle vmalloc() memory")
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reported-by: Zhen Lei <thunder.leizhen@huaweicloud.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Zqiang <qiang.zhang1211@gmail.com>
Cc: <stable@vger.kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 228a4a5..ef8599d 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4278,14 +4278,32 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
 #ifdef CONFIG_PRINTK
 bool vmalloc_dump_obj(void *object)
 {
-	struct vm_struct *vm;
 	void *objp = (void *)PAGE_ALIGN((unsigned long)object);
+	const void *caller;
+	struct vm_struct *vm;
+	struct vmap_area *va;
+	unsigned long addr;
+	unsigned int nr_pages;
 
-	vm = find_vm_area(objp);
-	if (!vm)
+	if (!spin_trylock(&vmap_area_lock))
+		return false;
+	va = __find_vmap_area((unsigned long)objp, &vmap_area_root);
+	if (!va) {
+		spin_unlock(&vmap_area_lock);
 		return false;
+	}
+
+	vm = va->vm;
+	if (!vm) {
+		spin_unlock(&vmap_area_lock);
+		return false;
+	}
+	addr = (unsigned long)vm->addr;
+	caller = vm->caller;
+	nr_pages = vm->nr_pages;
+	spin_unlock(&vmap_area_lock);
 	pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n",
-		vm->nr_pages, (unsigned long)vm->addr, vm->caller);
+		nr_pages, addr, caller);
 	return true;
 }
 #endif