On Wed, Jul 06, 2022 at 08:51:24AM +0300, Dan Carpenter wrote: > On Tue, Jul 05, 2022 at 03:06:49PM -0300, Jason Gunthorpe wrote: > > On Tue, Jul 05, 2022 at 12:05:28PM +0300, Dan Carpenter wrote: > > > The casting on this makes the integer overflow check slightly wrong. > > > "len" is an unsigned long. "*pos" and "requested_length" are signed > > > long longs. Imagine "len" is ULONG_MAX and "*pos" is 2. > > > "ULONG_MAX + 2 = 1". > > > > I wonder if this can happen, len is a kernel controlled value bounded > > by a memory allocation.. > > > > Oh. Smatch uses a model which says that all read/writes come from > vfs_write(). The problem with tracking kernel read/writes is that > recursion is tricky. So Smatch just deletes those from the DB. Oh, maybe I got it wrong, len is the user input, so yes that does look bad > > This code was copy and pasted from drivers/vfio/pci/mlx5/main.c, so it > > should be fixed too > > Sure. > > I created a static checker warning for this type of thing but it didn't > catch the issue in drivers/vfio/pci/mlx5/main.c because Smatch says that > the bug is impossible. Which is true. How come it is different? Jason
