linux-kernel - Re: [PATCH RESEND] floppy: fix open(O

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Message-ID: <08c74fa2-ecbf-3c1d-be09-2447bb009bcb@linux.com>
Date:   Thu, 21 Jan 2021 17:45:33 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, Wim Osterholt <wim@....tudelft.nl>
Subject: Re: [PATCH RESEND] floppy: fix open(O_ACCMODE) for ioctl-only open

On 1/21/21 1:25 PM, Jiri Kosina wrote:
> On Thu, 21 Jan 2021, Denis Efremov wrote:
> 
>> I think it's hard to recall the exact reasons after so many years. 
> 
> Yeah, I guess so :)
> 
>> I'll send a patch today based on this one.
> 
> I am currently waiting for confirmation by the original reporter that the 
> patch below fixes the issue.
> 
> 
> 
> From: Jiri Kosina <jkosina@...e.cz>
> Subject: [PATCH] floppy: reintroduce O_NDELAY fix
> 
> Originally fixed in 09954bad4 ("floppy: refactor open() flags handling")
> then reverted for unknown reason in f2791e7eadf437 instead of taking
> the open(O_ACCMODE) for ioctl-only open fix, which had the changelog below
> 
> ====
> Commit 09954bad4 ("floppy: refactor open() flags handling"), as a
> side-effect, causes open(/dev/fdX, O_ACCMODE) to fail. It turns out that
> this is being used setfdprm userspace for ioctl-only open().
> 
> Reintroduce back the original behavior wrt !(FMODE_READ|FMODE_WRITE)
> modes, while still keeping the original O_NDELAY bug fixed.
> 
> Cc: stable@...r.kernel.org # v4.5+
> Reported-by: Wim Osterholt <wim@....tudelft.nl>
> Tested-by: Wim Osterholt <wim@....tudelft.nl>
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> =====
> 
> Fixes: 09954bad4 ("floppy: refactor open() flags handling")
> Fixes: f2791e7ead ("Revert "floppy: refactor open() flags handling"")
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> ---
>  drivers/block/floppy.c | 29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index dfe1dfc901cc..bda9417aa0a8 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -4121,23 +4121,22 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)
>  	if (fdc_state[FDC(drive)].rawcmd == 1)
>  		fdc_state[FDC(drive)].rawcmd = 2;
>  
> -	if (!(mode & FMODE_NDELAY)) {
> -		if (mode & (FMODE_READ|FMODE_WRITE)) {
> -			drive_state[drive].last_checked = 0;
> -			clear_bit(FD_OPEN_SHOULD_FAIL_BIT,
> -				  &drive_state[drive].flags);
> -			if (bdev_check_media_change(bdev))
> -				floppy_revalidate(bdev->bd_disk);
> -			if (test_bit(FD_DISK_CHANGED_BIT, &drive_state[drive].flags))
> -				goto out;
> -			if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &drive_state[drive].flags))
> -				goto out;
> -		}
> -		res = -EROFS;
> -		if ((mode & FMODE_WRITE) &&
> -		    !test_bit(FD_DISK_WRITABLE_BIT, &drive_state[drive].flags))
> +	if (mode & (FMODE_READ|FMODE_WRITE)) {


As the bot points out this was refactored a bit in:
8d9d34e25a37 ("floppy: cleanup: expand macro UDRS")
4a6f3d480edc ("floppy: use bdev_check_media_change")

Should be something like:
+               drive_state[drive].last_checked = 0;
+               clear_bit(FD_OPEN_SHOULD_FAIL_BIT,
+                         &drive_state[drive].flags);
+               if (bdev_check_media_change(bdev))
+                       floppy_revalidate(bdev->bd_disk);

> +		if (test_bit(FD_DISK_CHANGED_BIT, &drive_state[drive].flags))
> +			goto out;
> +		if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &drive_state[drive].flags))
>  			goto out;
>  	}
> +
> +	res = -EROFS;
> +
> +	if ((mode & FMODE_WRITE) &&
> +			!test_bit(FD_DISK_WRITABLE_BIT, &drive_state[drive].flags))
> +		goto out;
> +
>  	mutex_unlock(&open_lock);
>  	mutex_unlock(&floppy_mutex);
>  	return 0;
>