linux-kernel - Re: [syzbot] [xfs?] [mm?] WARNING: bad unlock balance in __mm

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Message-ID: <tencent_3C336C9E411B294B141B23254FBAFFBB6208@qq.com>
Date: Thu,  6 Mar 2025 20:57:25 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+8f9f411152c9539f4e59@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [xfs?] [mm?] WARNING: bad unlock balance in __mm_populate

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git e056da87c780

diff --git a/mm/gup.c b/mm/gup.c
index 3883b307780e..9f740d607919 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1194,6 +1194,7 @@ static int faultin_page(struct vm_area_struct *vma,
 	}
 
 	ret = handle_mm_fault(vma, address, fault_flags, NULL);
+	printk("1mm: %p, map held lock: %d, vma: %p, %s\n", vma->vm_mm, lockdep_is_held(&vma->vm_mm->mmap_lock), vma, __func__);
 
 	if (ret & VM_FAULT_COMPLETED) {
 		/*
@@ -1216,8 +1217,11 @@ static int faultin_page(struct vm_area_struct *vma,
 	if (ret & VM_FAULT_ERROR) {
 		int err = vm_fault_to_errno(ret, flags);
 
-		if (err)
+		printk("mm: %p, map held lock: %d, vma: %p, err: %d, %s\n", vma->vm_mm, lockdep_is_held(&vma->vm_mm->mmap_lock), vma, err, __func__);
+		if (err) {
+			*locked = *locked ? err != -EFAULT : 0;
 			return err;
+		}
 		BUG();
 	}
 
@@ -1487,6 +1491,7 @@ static long __get_user_pages(struct mm_struct *mm,
 		cond_resched();
 
 		page = follow_page_mask(vma, start, gup_flags, &ctx);
+		printk("<after resched and follow page mask> mm: %p, map lock held: %d, %s\n", mm, lockdep_is_held(&mm->mmap_lock), __func__);
 		if (!page || PTR_ERR(page) == -EMLINK) {
 			ret = faultin_page(vma, start, gup_flags,
 					   PTR_ERR(page) == -EMLINK, locked);
@@ -1500,6 +1505,7 @@ static long __get_user_pages(struct mm_struct *mm,
 			case -EFAULT:
 			case -ENOMEM:
 			case -EHWPOISON:
+				printk("mm2: %p, map held lock: %d, vma: %p, ret: %d, %s\n", mm, lockdep_is_held(&mm->mmap_lock), vma, ret, __func__);
 				goto out;
 			}
 			BUG();
@@ -2029,7 +2035,12 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
 		 * double checks the vma flags, so that it won't mlock pages
 		 * if the vma was already munlocked.
 		 */
+		printk("1mm: %p, vma: %p, mmap lock held: %d, locked: %d, vma is acc: %d, %s\n",
+			mm, vma, lockdep_is_held(&mm->mmap_lock), locked, vma_is_accessible(vma), __func__);
 		ret = populate_vma_page_range(vma, nstart, nend, &locked);
+		printk("mm: %p, vma: %p, mmap lock held: %d, locked: %d, ret: %ld, mm addr is valid: %d, %s\n",
+			mm, vma, lockdep_is_held(&mm->mmap_lock), locked, ret, virt_addr_valid((void*)mm), __func__);
+
 		if (ret < 0) {
 			if (ignore_errors) {
 				ret = 0;
diff --git a/mm/memory.c b/mm/memory.c
index b4d3d4893267..43e35a0c2841 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6206,10 +6206,14 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
 
 	lru_gen_enter_fault(vma);
 
+	printk("mm: %p, map held lock: %d, vma: %p, is vm hugetlb page: %d, %s\n",
+		vma->vm_mm, lockdep_is_held(&vma->vm_mm->mmap_lock), vma, is_vm_hugetlb_page(vma), __func__);
 	if (unlikely(is_vm_hugetlb_page(vma)))
 		ret = hugetlb_fault(vma->vm_mm, vma, address, flags);
 	else
 		ret = __handle_mm_fault(vma, address, flags);
+	printk("2mm: %p, map held lock: %d, vma: %p, is vm hugetlb page: %d, %s\n",
+		vma->vm_mm, lockdep_is_held(&vma->vm_mm->mmap_lock), vma, is_vm_hugetlb_page(vma), __func__);
 
 	/*
 	 * Warning: It is no longer safe to dereference vma-> after this point,