Use f_lock to protect f_flags
Traditionally, changes to struct file->f_flags have been done under BKL
protection, or with no protection at all. This patch causes all f_flags
changes after file open/creation time to be done under protection of
f_lock. This allows the removal of some BKL usage and fixes a number of
longstanding (if microscopic) races.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index 1ab9dac..33bb76c 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -1711,7 +1711,9 @@
curlun->sense_data = SS_WRITE_PROTECTED;
return -EINVAL;
}
+ spin_lock(&curlun->filp->f_lock);
curlun->filp->f_flags &= ~O_SYNC; // Default is not to wait
+ spin_unlock(&curlun->filp->f_lock);
/* Get the starting Logical Block Address and check that it's
* not too big */
@@ -1728,8 +1730,11 @@
curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
return -EINVAL;
}
- if (fsg->cmnd[1] & 0x08) // FUA
+ if (fsg->cmnd[1] & 0x08) { // FUA
+ spin_lock(&curlun->filp->f_lock);
curlun->filp->f_flags |= O_SYNC;
+ spin_unlock(&curlun->filp->f_lock);
+ }
}
if (lba >= curlun->num_sectors) {
curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;