linux-kernel - [PATCH 6/5] block: check bdev_read_only() from blkdev

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Date:	Thu, 11 Nov 2010 18:10:17 +0100
From:	Tejun Heo <tj@...nel.org>
To:	axboe@...nel.dk, hch@...radead.org, linux-kernel@...r.kernel.org,
	petero2@...ia.com, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com, jack@...e.cz, akpm@...ux-foundation.org,
	adilger.kernel@...ger.ca, tytso@....edu, mfasheh@...e.com,
	joel.becker@...cle.com, aelder@....com, dm-devel@...hat.com,
	drbd-dev@...ts.linbit.com, neilb@...e.de, leochen@...adcom.com,
	sbranden@...adcom.com, chris.mason@...cle.com, swhiteho@...hat.com,
	shaggy@...ux.vnet.ibm.com, joern@...fs.org,
	konishi.ryusuke@....ntt.co.jp, reiserfs-devel@...r.kernel.org,
	viro@...iv.linux.org.uk, dbrownell@...rs.sourceforge.net
Subject: [PATCH 6/5] block: check bdev_read_only() from blkdev_get()

bdev read-only status can be queried using bdev_read_only() and may
change while the device is being opened.  Enforce it by checking it
from blkdev_get() after open succeeds.

This makes bdev_read_only() check in open_bdev_exclusive() and
fsg_lun_open() unnecessary.  Drop them.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: David Brownell <dbrownell@...rs.sourceforge.net>
Cc: linux-usb@...r.kernel.org
---
 drivers/usb/gadget/storage_common.c |    7 ++-----
 fs/block_dev.c                      |   11 ++++++-----
 2 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/drivers/usb/gadget/storage_common.c b/drivers/usb/gadget/storage_common.c
index 3b513ba..b015561 100644
--- a/drivers/usb/gadget/storage_common.c
+++ b/drivers/usb/gadget/storage_common.c
@@ -543,7 +543,7 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)
 	ro = curlun->initially_ro;
 	if (!ro) {
 		filp = filp_open(filename, O_RDWR | O_LARGEFILE, 0);
-		if (-EROFS == PTR_ERR(filp))
+		if (PTR_ERR(filp) == -EROFS || PTR_ERR(filp) == -EACCES)
 			ro = 1;
 	}
 	if (ro)
@@ -558,10 +558,7 @@ static int fsg_lun_open(struct fsg_lun *curlun, const char *filename)

 	if (filp->f_path.dentry)
 		inode = filp->f_path.dentry->d_inode;
-	if (inode && S_ISBLK(inode->i_mode)) {
-		if (bdev_read_only(inode->i_bdev))
-			ro = 1;
-	} else if (!inode || !S_ISREG(inode->i_mode)) {
+	if (!inode || (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))) {
 		LINFO(curlun, "invalid file type: %s\n", filename);
 		goto out;
 	}
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 269bfbb..606a525 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1149,6 +1149,12 @@ int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder)

 	res = __blkdev_get(bdev, mode, 0);

+	/* __blkdev_get() may alter read only status, check it afterwards */
+	if (!res && (mode & FMODE_WRITE) && bdev_read_only(bdev)) {
+		__blkdev_put(bdev, mode, 0);
+		res = -EACCES;
+	}
+
 	if (whole) {
 		/* finish claiming */
 		spin_lock(&bdev_lock);
@@ -1453,11 +1459,6 @@ struct block_device *open_bdev_exclusive(const char *path, fmode_t mode, void *h
 	if (error)
 		return ERR_PTR(error);

-	if ((mode & FMODE_WRITE) && bdev_read_only(bdev)) {
-		blkdev_put(bdev, mode);
-		return ERR_PTR(-EACCES);
-	}
-
 	return bdev;
 }

-- 
1.7.1

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