linux-kernel - Re: [syzbot] [mm?] kernel panic: corrupted stack end in userfaultfd

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Message-Id: <20240604123656.1730-1-hdanton@sina.com>
Date: Tue,  4 Jun 2024 20:36:56 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+5a1cb2c00e895afca87e@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] kernel panic: corrupted stack end in userfaultfd_ioctl

On Mon, 03 Jun 2024 06:05:33 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    4a4be1ad3a6e Revert "vfs: Delete the associated dentry whe..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15683162980000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master

--- a/arch/arm64/mm/contpte.c
+++ b/arch/arm64/mm/contpte.c
@@ -376,7 +376,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
 	 * clearing access/dirty for the whole block.
 	 */
 	unsigned long start = addr;
-	unsigned long end = start + nr;
+	unsigned long end = start + nr * PAGE_SIZE;
 
 	if (pte_cont(__ptep_get(ptep + nr - 1)))
 		end = ALIGN(end, CONT_PTE_SIZE);
@@ -386,7 +386,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
 		ptep = contpte_align_down(ptep);
 	}
 
-	__clear_young_dirty_ptes(vma, start, ptep, end - start, flags);
+	__clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_SIZE, flags);
 }
 EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);
 
--