This is a second version of the patch set. The only change is in 2/4 x86: add phys addr validity check for /dev/mem mmap where the "count" was replaced with "len_bytes" for better readability. The rest is just a refresh because of this change. The original message follows ... Hi all, this is a combination of two patch sets I sent a while ago 1) Prevent possible PTE corruption with /dev/mem mmap 2) x86: allow read/write /dev/mem to access non-system RAM above high_memory The original thread with both patch sets can be found here https://lkml.org/lkml/2014/8/14/229 lkml: <1408025927-16826-1-git-send-email-fhrbata@xxxxxxxxxx> 1) Prevent possible PTE corruption with /dev/mem mmap x86: add arch_pfn_possible helper x86: add phys addr validity check for /dev/mem mmap Many thanks goes to Dave Hansen, who helped with the "final" check. Other than that it did not get much attention, except H. Peter Anvin's complain that having two checks for mmap and read/write for /dev/mem access is ridiculous. I for sure do not object to this, but AFAICT it's not that simple to unify them and it's not "directly" related to the PTE corruption. Please note that there are other archs(ia64, arm) using these check. But I for sure can be missing something. What this patch set does is using the existing interface to implement x86 specific check in the least invasive way. Anyway I tried to remove the high_memory check with a follow-up patch set 2) 2) x86: allow read/write /dev/mem to access non-system RAM above high_memory x86: add high_memory check to (xlate|unxlate)_dev_mem_ptr x86: remove high_memory check from valid_phys_addr_range This is an attempt to remove the high_memory limit for the read/write access to /dev/mem. IMHO there is no reason for this limit on x86. It is presented in the generic valid_phys_addr_range, which is used only by (read|write)_mem. IIUIC it's main purpose is for the generic xlate_dev_mem_ptr, which is using only the direct kernel mapping __va translation. Since the valid_phys_addr_range is called as the first check in (read|write)_mem, it basically does not allow to access anything above high_memory on x86. The first patch adds high_memory check to x86's (xlate|unxlate)_dev_mem_ptr, so the direct kernel mapping can be safely used for system RAM bellow high_memory. This is IMHO the only valid reason to use high_memory check in (read|write)_mem. The second patch removes the high_memory check from valid_phys_addr_range, allowing read/write to access non-system RAM above high_memory. So far this was possible only by using mmap. I hope I haven't overlooked something. Many thanks Frantisek Hrbata (4): x86: add arch_pfn_possible helper x86: add phys addr validity check for /dev/mem mmap x86: add high_memory check to (xlate|unxlate)_dev_mem_ptr x86: remove high_memory check from valid_phys_addr_range arch/x86/include/asm/io.h | 4 ++++ arch/x86/mm/ioremap.c | 9 ++++++--- arch/x86/mm/mmap.c | 12 ++++++++++++ arch/x86/mm/physaddr.h | 9 +++++++-- 4 files changed, 29 insertions(+), 5 deletions(-) -- 1.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>