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@kernel.org>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: linux-usb@vger.kernel.org

diff --git a/drivers/usb/gadget/storage_common.c b/drivers/usb/gadget/storage_common.c
index 3b513bafaf2a43dac58f0dc87e0ddde6f28dd601..b015561fd602a526d6c76aa52cff3a04f94d026e 100644 (file)
--- 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 269bfbbd10fcb9c2e7c450e9ac548fd787dc5721..606a5259f87fc9c8dfc146f990d84af6ad613dd1 100644 (file)
--- 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;
 }