linux-kernel - Re: [syzbot] [nilfs?] [mm?] KASAN: slab-use-after-free Read in lru_add

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Date: Thu, 13 Jun 2024 18:57:41 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+d79afb004be235636ee8@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [nilfs?] [mm?] KASAN: slab-use-after-free Read in lru_add_fn

On Tue, 11 Jun 2024 11:10:20 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    83a7eefedc9b Linux 6.10-rc3
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17c645e2980000

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

--- x/fs/read_write.c
+++ y/fs/read_write.c
@@ -570,6 +570,7 @@ EXPORT_SYMBOL(kernel_write);
 ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 {
 	ssize_t ret;
+	struct super_block *sb;
 
 	if (!(file->f_mode & FMODE_WRITE))
 		return -EBADF;
@@ -583,6 +584,9 @@ ssize_t vfs_write(struct file *file, con
 		return ret;
 	if (count > MAX_RW_COUNT)
 		count =  MAX_RW_COUNT;
+	sb = file_inode(file)->i_sb;
+	if (!down_read_trylock(&sb->s_umount))
+		return -EINVAL;
 	file_start_write(file);
 	if (file->f_op->write)
 		ret = file->f_op->write(file, buf, count, pos);
@@ -596,6 +600,7 @@ ssize_t vfs_write(struct file *file, con
 	}
 	inc_syscw(current);
 	file_end_write(file);
+	up_read(&sb->s_umount);
 	return ret;
 }
 
--