linux-kernel - Re: [syzbot] KASAN: use-after-free Read in disk_part_iter

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Date:   Mon, 22 Mar 2021 08:18:01 +0100
From:   Christoph Hellwig <hch@....de>
To:     syzbot <syzbot+8fede7e30c7cee0de139@...kaller.appspotmail.com>
Cc:     axboe@...nel.dk, hch@....de, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        tj@...nel.org
Subject: Re: [syzbot] KASAN: use-after-free Read in disk_part_iter_next (2)

I've been running the reproducer on a KASAN enable VM for about
15 minutes now, but haven't been able to reproduce it.

Is there a way to inject this proposed fix into the syzbot queue?

diff --git a/block/partitions/core.c b/block/partitions/core.c
index 1a7558917c47d6..f5d5872b89d57e 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -288,15 +288,12 @@ struct device_type part_type = {
 void delete_partition(struct block_device *part)
 {
 	xa_erase(&part->bd_disk->part_tbl, part->bd_partno);
-	kobject_put(part->bd_holder_dir);
-	device_del(&part->bd_device);
-
-	/*
-	 * Remove the block device from the inode hash, so that it cannot be
-	 * looked up any more even when openers still hold references.
-	 */
 	remove_inode_hash(part->bd_inode);
 
+	synchronize_rcu();
+
+	kobject_put(part->bd_holder_dir);
+	device_del(&part->bd_device);
 	put_device(&part->bd_device);
 }