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Subject[PATCH] fs/locks.c fcntl_setlease did not check if a file was opened for writing before granting a read lease
Date
Gee, that seemed simple enough.

Keep in mind that I'm new to this whole 'kernel development' thing, and I offer no assurance that my patch actually works. I only know that it compiles without errors or warnings.

But I THINK this is how a patch would fix the problem, in theory.

This is where the 'theory of a thousand eyes' is going to have to help me out.

TIA guys.

BTW, this patch should be applied to both the 2.4 and 2.6 series of kernels (if it works).

Joseph D. Wagner

--- /old/linux-2.4.22/fs/locks.c 2003-08-25 17:44:43.000000000 +0600
+++ /new/linux-2.4.22/fs/locks.c 2003-11-27 10:08:41.000000000 +0600
@@ -111,10 +111,16 @@
* Matthew Wilcox <willy@thepuffingroup.com>, March, 2000.
*
* Leases and LOCK_MAND
* Matthew Wilcox <willy@linuxcare.com>, June, 2000.
* Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
+ *
+ * FIXED Leases Issue -- Function fcntl_setlease would only check if a
+ * file had been opened before granting a F_WRLCK, a.k.a. a write lease.
+ * It would not check if the file had be opened for writing before
+ * granting a F_RDLCK, a.k.a. a read lease. This issue is now resolved.
+ * Joseph D. Wagner <wagnerjd@users.sourceforge.net> November 2003
*/

#include <linux/slab.h>
#include <linux/file.h>
#include <linux/smp_lock.h>
@@ -1287,18 +1293,25 @@

lock_kernel();

time_out_leases(inode);

- /*
- * FIXME: What about F_RDLCK and files open for writing?
- */
error = -EAGAIN;
if ((arg == F_WRLCK)
&& ((atomic_read(&dentry->d_count) > 1)
|| (atomic_read(&inode->i_count) > 1)))
goto out_unlock;
+ if ((arg == F_RDLCK)
+ && ((dentry->d_flags & O_WRONLY)
+ || (dentry->d_flags & O_RDWR)
+ || (dentry->d_flags & O_CREAT)
+ || (dentry->d_flags & O_TRUNC)
+ || (inode->i_flags & O_WRONLY)
+ || (inode->i_flags & O_RDWR)
+ || (inode->i_flags & O_CREAT)
+ || (inode->i_flags & O_TRUNC)))
+ goto out_unlock;

/*
* At this point, we know that if there is an exclusive
* lease on this file, then we hold it on this filp
* (otherwise our open of this file would have blocked).
-
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