On Fri, Jul 13, 2012 at 10:47:43AM -0700, Linus Torvalds wrote:
> On Fri, Jul 13, 2012 at 10:35 AM, Dave Jones <da...@redhat.com> wrote:
> > This can be trivially triggered from userspace by passing in something
> > unexpected.
>
> Argh. It looks like it would be harmless (apart from the noise),
> except we hold file_lock_lock. Which turns the BUG_ON() into not just
> "noise and kill the process", but "noise and kill the process and
> leave a nasty lock held".
>
> This seems to go back to 3.2, so stable should be cc'd, no?
Thanks! Yes, this fixes the bug for >=3.2, but before the addition of
this BUG() we could get memory corruption in this case. And that
problem existed since the original introduction of the lease code, as
far as I can tell.
So we need something like the following, backported to 2.6.anything.
--b.
commit 76fca57d7f4e408fc758a42f798c2ebef54be60f
Author: J. Bruce Fields <bfie...@redhat.com>
Date: Wed Jul 18 17:45:42 2012 -0600
locks: fix checking of fcntl_setlease argument
The only checks of the long argument passed to fcntl(fd,F_SETLEASE,.)
are done after converting the long to an int. Thus some illegal values
may be let through and cause problems in later code.
Cc: sta...@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfie...@redhat.com>
diff --git a/fs/locks.c b/fs/locks.c
index 43797a9..ad1de47 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -311,7 +311,7 @@ static int flock_make_lock(struct file *filp, struct
file_lock **lock,
return 0;
}
-static int assign_type(struct file_lock *fl, int type)
+static int assign_type(struct file_lock *fl, long type)
{
switch (type) {
case F_RDLCK:
@@ -448,7 +448,7 @@ static const struct lock_manager_operations
lease_manager_ops = {
/*
* Initialize a lease, use the default lock manager operations
*/
-static int lease_init(struct file *filp, int type, struct file_lock *fl)
+static int lease_init(struct file *filp, long type, struct file_lock *fl)
{
if (assign_type(fl, type) != 0)
return -EINVAL;
@@ -466,7 +466,7 @@ static int lease_init(struct file *filp, int type, struct
file_lock *fl)
}
/* Allocate a file_lock initialised to this type of lease */
-static struct file_lock *lease_alloc(struct file *filp, int type)
+static struct file_lock *lease_alloc(struct file *filp, long type)
{
struct file_lock *fl = locks_alloc_lock();
int error = -ENOMEM;
--
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