On Fri, Feb 07, 2025 at 10:42:34AM +1100, Balbir Singh wrote: > When CONFIG_PCI_P2PDMA is enabled, it maps the PFN's via a > ZONE_DEVICE mapping using devm_memremap_pages(). The mapped > virtual address range corresponds to the pci_resource_start() > of the BAR address and size corresponding to the BAR length. > > When KASLR is enabled, the direct map range of the kernel is > reduced to the size of physical memory plus additional padding. > If the BAR address is beyond this limit, PCI peer to peer DMA > mappings fail. > > Fix this by not shrinking the size of direct map when CONFIG_PCI_P2PDMA > is enabled. This reduces the total available entropy, but it's > better than the current work around of having to disable KASLR > completely. > > Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxxxx> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Cc: Kees Cook <kees@xxxxxxxxxx> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Link: https://lore.kernel.org/lkml/20250206023201.1481957-1-balbirs@xxxxxxxxxx/ > > Signed-off-by: Balbir Singh <balbirs@xxxxxxxxxx> Thanks for the update! Reviewed-by: Kees Cook <kees@xxxxxxxxxx> -- Kees Cook
