On Sun, 22 Jan 2023 11:57:58 +0100 Greg KH gregkh@linuxfoundation.org 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@linux.intel.com Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Cc: stable@vger.kernel.org
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.
- 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