On Sun, 22 Jan 2023 11:57:58 +0100 Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Sun, Jan 22, 2023 at 11:00:04AM +0200, Leon Romanovsky wrote: > > On Thu, Jan 19, 2023 at 07:06:32PM +0200, Alexander Shishkin wrote: > > > A malicious device can change its MSIX table size between the table > > > ioremap() and subsequent accesses, resulting in a kernel page fault in > > > pci_write_msg_msix(). > > > > > > To avoid this, cache the table size observed at the moment of table > > > ioremap() and use the cached value. This, however, does not help drivers > > > that peek at the PCIE_MSIX_FLAGS register directly. > > > > > > Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx> > > > Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > > > Cc: stable@xxxxxxxxxxxxxxx > > > --- > > > drivers/pci/msi/api.c | 7 ++++++- > > > drivers/pci/msi/msi.c | 2 +- > > > include/linux/pci.h | 1 + > > > 3 files changed, 8 insertions(+), 2 deletions(-) > > > > I'm not security expert here, but not sure that this protects from anything. > > 1. Kernel relies on working and not-malicious HW. There are gazillion ways > > to cause crashes other than changing MSI-X. > > Linux does NOT protect from malicious PCIe devices at this point in > time, you are correct. If we wish to change that model, then we can > work on that with the explict understanding that most all drivers will > need to change as will the bus logic for the busses involved. > > To do piece-meal patches like this for no good reason is not a good idea > as it achieves nothing in the end :( > > thanks, > > greg k-h If you care enough about potential malicious PCIe devices, do device attestation and reject any devices that don't support it (which means rejecting pretty much everything today ;). Or potentially limit what non attested devices are allowed to do. +CC Lukas who is working on this. Jonathan
