On Tue, Jan 24, 2023 at 01:52:37PM +0200, Alexander Shishkin wrote:
Leon Romanovsky leon@kernel.org writes:
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.
This particular bug was preventing our fuzzing from going deeper into the code and reaching some more of the aforementioned gazillion bugs.
As per our documentation, if you are "fixing" things based on a tool you have, you HAVE TO document that in the changelog. Otherwise we just get to reject the patch flat out (hint, this has caused more than one group of developers to just be flat out banned for ignoring...)
And what kind of tool is now fuzzing PCI config accesses with "malicious" devices? Again, this is NOT something that Linux currently even attempts to want to protect itself against. If you are wanting to change that model, wonderful, let's discuss that and work on defining the scope of your new security threat model and go from there. Don't throw random patches at us and expect us to think they are even valid.
Again, Linux trusts PCI devices. If you don't want to trust PCI devices, we already have a framework in place to prevent that which is independant of this area of the PCI code. Use that, or let's discuss why that is insufficient.
Sure, I have started a new thread on this in https://lore.kernel.org/all/DM8PR11MB57505481B2FE79C3D56C9201E7CE9@DM8PR11MB...
I think it is much bigger topic to discuss, so better be handled separately.
Best Regards, Elena.