Hi Yang,
On Fri, 1 Oct 2021 at 03:23, Yang Shi shy828301@gmail.com wrote:
When handling shmem page fault the THP with corrupted subpage could be PMD mapped if certain conditions are satisfied. But kernel is supposed to send SIGBUS when trying to map hwpoisoned page.
There are two paths which may do PMD map: fault around and regular fault.
Before commit f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths") the thing was even worse in fault around path. The THP could be PMD mapped as long as the VMA fits regardless what subpage is accessed and corrupted. After this commit as long as head page is not corrupted the THP could be PMD mapped.
In the regular fault path the THP could be PMD mapped as long as the corrupted page is not accessed and the VMA fits.
This loophole could be fixed by iterating every subpage to check if any of them is hwpoisoned or not, but it is somewhat costly in page fault path.
So introduce a new page flag called HasHWPoisoned on the first tail page. It indicates the THP has hwpoisoned subpage(s). It is set if any subpage of THP is found hwpoisoned by memory failure and cleared when the THP is freed or split.
Fixes: 800d8c63b2e9 ("shmem: add huge pages support") Cc: stable@vger.kernel.org Suggested-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Yang Shi shy828301@gmail.com
include/linux/page-flags.h | 19 +++++++++++++++++++ mm/filemap.c | 12 ++++++------ mm/huge_memory.c | 2 ++ mm/memory-failure.c | 6 +++++- mm/memory.c | 9 +++++++++ mm/page_alloc.c | 4 +++- 6 files changed, 44 insertions(+), 8 deletions(-)
When CONFIG_MEMORY_FAILURE not set we get these build failures.
Regression found on x86_64 and i386 gcc-11 builds Following build warnings / errors reported on Linux mainline master.
metadata: git_describe: v5.15-559-g19901165d90f git_repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git_short_log: 19901165d90f ("Merge tag 'for-5.16/inode-sync-2021-10-29' of git://git.kernel.dk/linux-block") target_arch: x86_64 toolchain: gcc-11
In file included from include/linux/mmzone.h:22, from include/linux/gfp.h:6, from include/linux/slab.h:15, from include/linux/crypto.h:20, from arch/x86/kernel/asm-offsets.c:9: include/linux/page-flags.h:806:29: error: macro "PAGEFLAG_FALSE" requires 2 arguments, but only 1 given 806 | PAGEFLAG_FALSE(HasHWPoisoned) | ^ include/linux/page-flags.h:411: note: macro "PAGEFLAG_FALSE" defined here 411 | #define PAGEFLAG_FALSE(uname, lname) TESTPAGEFLAG_FALSE(uname, lname) \ | include/linux/page-flags.h:807:39: error: macro "TESTSCFLAG_FALSE" requires 2 arguments, but only 1 given 807 | TESTSCFLAG_FALSE(HasHWPoisoned) | ^ include/linux/page-flags.h:414: note: macro "TESTSCFLAG_FALSE" defined here 414 | #define TESTSCFLAG_FALSE(uname, lname) \ | include/linux/page-flags.h:806:1: error: unknown type name 'PAGEFLAG_FALSE' 806 | PAGEFLAG_FALSE(HasHWPoisoned) | ^~~~~~~~~~~~~~ include/linux/page-flags.h:807:25: error: expected ';' before 'static' 807 | TESTSCFLAG_FALSE(HasHWPoisoned) | ^ | ; ...... 815 | static inline bool is_page_hwpoison(struct page *page) | ~~~~~~ make[2]: *** [scripts/Makefile.build:121: arch/x86/kernel/asm-offsets.s] Error 1
Reported-by: Linux Kernel Functional Testing lkft@linaro.org
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