linux-kernel - Re: [syzbot] [block?] possible deadlock in loop_set

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Message-ID: <20250301134743.2874-1-hdanton@sina.com>
Date: Sat,  1 Mar 2025 21:47:39 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+9b145229d11aa73e4571@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [block?] possible deadlock in loop_set_status

On Sat, 01 Mar 2025 02:18:23 -0800
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    276f98efb64a Merge tag 'block-6.14-20250228' of git://git...
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14f2c864580000

#syz test

--- x/drivers/block/loop.c
+++ y/drivers/block/loop.c
@@ -1286,17 +1286,16 @@ loop_set_status(struct loop_device *lo,
 	lo->lo_flags &= ~LOOP_SET_STATUS_CLEARABLE_FLAGS;
 	lo->lo_flags |= (info->lo_flags & LOOP_SET_STATUS_SETTABLE_FLAGS);
 
-	if (size_changed) {
-		loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
-					   lo->lo_backing_file);
-		loop_set_size(lo, new_size);
-	}
-
 	/* update the direct I/O flag if lo_offset changed */
 	loop_update_dio(lo);
 
 out_unfreeze:
 	blk_mq_unfreeze_queue(lo->lo_queue, memflags);
+	if (!err && size_changed) {
+		loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
+					   lo->lo_backing_file);
+		loop_set_size(lo, new_size);
+	}
 	if (partscan)
 		clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
 out_unlock:
--