This is a note to let you know that I've just added the patch titled
block: increment diskseq on all media change events
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
block-increment-diskseq-on-all-media-change-events.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b90ecc0379eb7bbe79337b0c7289390a98752646 Mon Sep 17 00:00:00 2001
From: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 7 Jun 2023 13:08:37 -0400
Subject: block: increment diskseq on all media change events
From: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
commit b90ecc0379eb7bbe79337b0c7289390a98752646 upstream.
Currently, associating a loop device with a different file descriptor
does not increment its diskseq. This allows the following race
condition:
1. Program X opens a loop device
2. Program X gets the diskseq of the loop device.
3. Program X associates a file with the loop device.
4. Program X passes the loop device major, minor, and diskseq to
something.
5. Program X exits.
6. Program Y detaches the file from the loop device.
7. Program Y attaches a different file to the loop device.
8. The opener finally gets around to opening the loop device and checks
that the diskseq is what it expects it to be. Even though the
diskseq is the expected value, the result is that the opener is
accessing the wrong file.
>From discussions with Christoph Hellwig, it appears that
disk_force_media_change() was supposed to call inc_diskseq(), but in
fact it does not. Adding a Fixes: tag to indicate this. Christoph's
Reported-by is because he stated that disk_force_media_change()
calls inc_diskseq(), which is what led me to discover that it should but
does not.
Reported-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
Fixes: e6138dc12de9 ("block: add a helper to raise a media changed event")
Cc: stable@xxxxxxxxxxxxxxx # 5.15+
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Link: https://lore.kernel.org/r/20230607170837.1559-1-demi@xxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/disk-events.c | 1 +
1 file changed, 1 insertion(+)
--- a/block/disk-events.c
+++ b/block/disk-events.c
@@ -307,6 +307,7 @@ bool disk_force_media_change(struct gend
if (!(events & DISK_EVENT_MEDIA_CHANGE))
return false;
+ inc_diskseq(disk);
if (__invalidate_device(disk->part0, true))
pr_warn("VFS: busy inodes on changed media %s\n",
disk->disk_name);
Patches currently in stable-queue which might be from demi@xxxxxxxxxxxxxxxxxxxxxx are
queue-6.4/block-increment-diskseq-on-all-media-change-events.patch
