Messages in this thread Patch in this message | | | Date | Mon, 23 Jul 2012 11:20:39 -0400 | Subject | Re: Remove easily user-triggerable BUG from generic_setlease | From | "J. Bruce Fields" <> |
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On Fri, Jul 13, 2012 at 10:47:43AM -0700, Linus Torvalds wrote: > On Fri, Jul 13, 2012 at 10:35 AM, Dave Jones <davej@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 <bfields@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: stable@vger.kernel.org Signed-off-by: J. Bruce Fields <bfields@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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