[PATCH] 2.4.9-ac10 but not only, locks_alloc_lock()

[PATCH] 2.4.9-ac10 but not only, locks_alloc_lock()

[Francis Galiegue]

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Also affects: 2.4.7, 2.4.9-ac{4,6,9}, probably others.

Problem: in locks_mandatory_area(), fcntl_setlk(), fcntl_setlk64(), no
check whether locks_alloc_lock() succeeds. Attached patch fixes that.

Not sure about one thing, though: what error code to return for
locks_mandatory_area() on failure. It's invoked from some of the
{do,sys}_*{read,write}*() routines and nowhere else AFAICT. I set it to
-ENOMEM, maybe this is not the right thing to do.

Patch follows and is attached. Made over 2.4.9-ac10, applies cleanly
over -ac's mentioned above and with offests (1 to 3 lines) on 2.4.7 and
2.4.9.


diff -urN linux-old/fs/locks.c linux/fs/locks.c
--- linux-old/fs/locks.c	Sun Sep  9 09:00:06 2001
+++ linux/fs/locks.c	Sun Sep  9 09:21:07 2001
@@ -698,6 +698,9 @@
 	struct file_lock *new_fl = locks_alloc_lock(0);
 	int error;

+	if (new_fl == NULL)
+		return -ENOMEM;
+
 	new_fl->fl_owner = current->files;
 	new_fl->fl_pid = current->pid;
 	new_fl->fl_file = filp;
@@ -1411,6 +1414,9 @@
 	struct inode *inode;
 	int error;

+	if (file_lock == NULL)
+		return -ENOLCK;
+
 	/*
 	 * This might block, so we do it before checking the inode.
 	 */
@@ -1563,6 +1569,9 @@
 	struct flock64 flock;
 	struct inode *inode;
 	int error;
+
+	if (file_lock == NULL)
+		return -ENOLCK;

 	/*
 	 * This might block, so we do it before checking the inode.

-- 
Francis Galiegue, fg@mandrakesoft.com - Normand et fier de l'être
"Programming is a race between programmers, who try and make more and more
idiot-proof software, and universe, which produces more and more remarkable
idiots. Until now, universe leads the race"  -- R. Cook

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diff -urN linux-old/fs/locks.c linux/fs/locks.c
--- linux-old/fs/locks.c	Sun Sep  9 09:00:06 2001
+++ linux/fs/locks.c	Sun Sep  9 09:21:07 2001
@@ -698,6 +698,9 @@
 	struct file_lock *new_fl = locks_alloc_lock(0);
 	int error;
 
+	if (new_fl == NULL)
+		return -ENOMEM;
+
 	new_fl->fl_owner = current->files;
 	new_fl->fl_pid = current->pid;
 	new_fl->fl_file = filp;
@@ -1411,6 +1414,9 @@
 	struct inode *inode;
 	int error;
 
+	if (file_lock == NULL)
+		return -ENOLCK;
+
 	/*
 	 * This might block, so we do it before checking the inode.
 	 */
@@ -1563,6 +1569,9 @@
 	struct flock64 flock;
 	struct inode *inode;
 	int error;
+
+	if (file_lock == NULL)
+		return -ENOLCK;
 
 	/*
 	 * This might block, so we do it before checking the inode.

Re: [PATCH] 2.4.9-ac10 but not only, locks_alloc_lock()

[Manfred Spraul]

> Not sure about one thing, though: what error code to return for
> locks_mandatory_area() on failure. It's invoked from some of the
> {do,sys}_*{read,write}*() routines and nowhere else AFAICT. I set it
to
> -ENOMEM, maybe this is not the right thing to do.

I'd put the file_lock structure on the stack. It's ~ 90 bytes long, not
too large.
Returning -ENOMEM is imho not acceptable: -ENOMEM is not listed in
SusV2, and locks_alloc_lock() internally checks for rlimits (setting
RLIM_NLIMITS to 0 and execing another app might have dangerous
sideeffects).

--
    Manfred

Re: [PATCH] 2.4.9-ac10 but not only, locks_alloc_lock()

[Francis Galiegue]

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On Sun, 9 Sep 2001, Manfred Spraul wrote:

>
> > Not sure about one thing, though: what error code to return for
> > locks_mandatory_area() on failure. It's invoked from some of the
> > {do,sys}_*{read,write}*() routines and nowhere else AFAICT. I set it
> > to -ENOMEM, maybe this is not the right thing to do.
>
> I'd put the file_lock structure on the stack. It's ~ 90 bytes long, not
> too large.
> Returning -ENOMEM is imho not acceptable: -ENOMEM is not listed in
> SusV2, and locks_alloc_lock() internally checks for rlimits (setting
> RLIM_NLIMITS to 0 and execing another app might have dangerous
> sideeffects).
>

Not sure about what you mean wrt RLIM_NLIMITS, anyway a new patch is
attached with follows your suggestion. Does it look correct?

-- 
Francis Galiegue, fg@mandrakesoft.com - Normand et fier de l'être
"Programming is a race between programmers, who try and make more and more
idiot-proof software, and universe, which produces more and more remarkable
idiots. Until now, universe leads the race"  -- R. Cook

[-- Attachment #2: Type: TEXT/PLAIN, Size: 2124 bytes --]

diff -urN linux-old/fs/locks.c linux/fs/locks.c
--- linux-old/fs/locks.c	Sun Sep  9 09:00:06 2001
+++ linux/fs/locks.c	Sun Sep  9 12:12:02 2001
@@ -695,16 +695,18 @@
 			 size_t count)
 {
 	struct file_lock *fl;
-	struct file_lock *new_fl = locks_alloc_lock(0);
+	struct file_lock new_fl;
 	int error;
 
-	new_fl->fl_owner = current->files;
-	new_fl->fl_pid = current->pid;
-	new_fl->fl_file = filp;
-	new_fl->fl_flags = FL_POSIX | FL_ACCESS;
-	new_fl->fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
-	new_fl->fl_start = offset;
-	new_fl->fl_end = offset + count - 1;
+	memset(&new_fl, 0, sizeof(new_fl));
+	
+	new_fl.fl_owner = current->files;
+	new_fl.fl_pid = current->pid;
+	new_fl.fl_file = filp;
+	new_fl.fl_flags = FL_POSIX | FL_ACCESS;
+	new_fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
+	new_fl.fl_start = offset;
+	new_fl.fl_end = offset + count - 1;
 
 	error = 0;
 	lock_kernel();
@@ -716,17 +718,17 @@
 	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
 		if (!(fl->fl_flags & FL_POSIX))
 			continue;
-		if (fl->fl_start > new_fl->fl_end)
+		if (fl->fl_start > new_fl.fl_end)
 			break;
-		if (posix_locks_conflict(new_fl, fl)) {
+		if (posix_locks_conflict(&new_fl, fl)) {
 			error = -EAGAIN;
 			if (filp && (filp->f_flags & O_NONBLOCK))
 				break;
 			error = -EDEADLK;
-			if (posix_locks_deadlock(new_fl, fl))
+			if (posix_locks_deadlock(&new_fl, fl))
 				break;
 	
-			error = locks_block_on(fl, new_fl);
+			error = locks_block_on(fl, &new_fl);
 			if (error != 0)
 				break;
 	
@@ -739,7 +741,6 @@
 			goto repeat;
 		}
 	}
-	locks_free_lock(new_fl);
 	unlock_kernel();
 	return error;
 }
@@ -1411,6 +1412,9 @@
 	struct inode *inode;
 	int error;
 
+	if (file_lock == NULL)
+		return -ENOLCK;
+
 	/*
 	 * This might block, so we do it before checking the inode.
 	 */
@@ -1563,6 +1567,9 @@
 	struct flock64 flock;
 	struct inode *inode;
 	int error;
+
+	if (file_lock == NULL)
+		return -ENOLCK;
 
 	/*
 	 * This might block, so we do it before checking the inode.