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. 1. Kernel relies on working and not-malicious HW. There are gazillion ways to cause crashes other than changing MSI-X. 2. Device can report large table size, kernel will cache it and malicious device will reduce it back. It is not handled and will cause to kernel crash too.
Thanks
diff --git a/drivers/pci/msi/api.c b/drivers/pci/msi/api.c index b8009aa11f3c..617ea1256487 100644 --- a/drivers/pci/msi/api.c +++ b/drivers/pci/msi/api.c @@ -75,8 +75,13 @@ int pci_msix_vec_count(struct pci_dev *dev) if (!dev->msix_cap) return -EINVAL;
- if (dev->flags_qsize)
return dev->flags_qsize;- pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control);
- return msix_table_size(control);
- dev->flags_qsize = msix_table_size(control);
- return dev->flags_qsize;
} EXPORT_SYMBOL(pci_msix_vec_count); diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c index 1f716624ca56..d50cd45119f1 100644 --- a/drivers/pci/msi/msi.c +++ b/drivers/pci/msi/msi.c @@ -715,7 +715,7 @@ static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries, pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control); /* Request & Map MSI-X table region */
- tsize = msix_table_size(control);
- tsize = pci_msix_vec_count(dev); dev->msix_base = msix_map_region(dev, tsize); if (!dev->msix_base) { ret = -ENOMEM;
diff --git a/include/linux/pci.h b/include/linux/pci.h index adffd65e84b4..2e1a72a2139d 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -352,6 +352,7 @@ struct pci_dev { u8 rom_base_reg; /* Config register controlling ROM */ u8 pin; /* Interrupt pin this device uses */ u16 pcie_flags_reg; /* Cached PCIe Capabilities Register */
- u16 flags_qsize; /* Cached MSIX table size */ unsigned long *dma_alias_mask;/* Mask of enabled devfn aliases */
struct pci_driver *driver; /* Driver bound to this device */ -- 2.39.0