[PATCH 5.4 290/340] floppy: reintroduce O_NDELAY fix

[Greg Kroah-Hartman]

From: Jiri Kosina <jkosina@xxxxxxx>

commit 8a0c014cd20516ade9654fc13b51345ec58e7be8 upstream.

This issue was originally fixed in 09954bad4 ("floppy: refactor open()
flags handling").

The fix as a side-effect, however, introduce issue for open(O_ACCMODE)
that is being used for ioctl-only open. I wrote a fix for that, but
instead of it being merged, full revert of 09954bad4 was performed,
re-introducing the O_NDELAY / O_NONBLOCK issue, and it strikes again.

This is a forward-port of the original fix to current codebase; the
original submission 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.

Link: https://lore.kernel.org/r/nycvar.YFH.7.76.2101221209060.5622@xxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Wim Osterholt <wim@xxxxxxxxxxxxxx>
Tested-by: Wim Osterholt <wim@xxxxxxxxxxxxxx>
Reported-and-tested-by: Kurt Garloff <kurt@xxxxxxxxxx>
Fixes: 09954bad4 ("floppy: refactor open() flags handling")
Fixes: f2791e7ead ("Revert "floppy: refactor open() flags handling"")
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Denis Efremov <efremov@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/block/floppy.c |   27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -4063,21 +4063,22 @@ static int floppy_open(struct block_devi
 	if (UFDCS->rawcmd == 1)
 		UFDCS->rawcmd = 2;
 
-	if (!(mode & FMODE_NDELAY)) {
-		if (mode & (FMODE_READ|FMODE_WRITE)) {
-			UDRS->last_checked = 0;
-			clear_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags);
-			check_disk_change(bdev);
-			if (test_bit(FD_DISK_CHANGED_BIT, &UDRS->flags))
-				goto out;
-			if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags))
-				goto out;
-		}
-		res = -EROFS;
-		if ((mode & FMODE_WRITE) &&
-		    !test_bit(FD_DISK_WRITABLE_BIT, &UDRS->flags))
+	if (mode & (FMODE_READ|FMODE_WRITE)) {
+		UDRS->last_checked = 0;
+		clear_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags);
+		check_disk_change(bdev);
+		if (test_bit(FD_DISK_CHANGED_BIT, &UDRS->flags))
+			goto out;
+		if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags))
 			goto out;
 	}
+
+	res = -EROFS;
+
+	if ((mode & FMODE_WRITE) &&
+			!test_bit(FD_DISK_WRITABLE_BIT, &UDRS->flags))
+		goto out;
+
 	mutex_unlock(&open_lock);
 	mutex_unlock(&floppy_mutex);
 	return 0;