kernel/linux.git/mm/page_table_check.c, branch v6.12.91

mm/page_table_check: fix crash on ZONE_DEVICE

2024-06-15T17:43:04+00:00

Not all pages may apply to pgtable check. One example is ZONE_DEVICE pages: they map PFNs directly, and they don't allocate page_ext at all even if there's struct page around. One may reference devm_memremap_pages(). When both ZONE_DEVICE and page-table-check enabled, then try to map some dax memories, one can trigger kernel bug constantly now when the kernel was trying to inject some pfn maps on the dax device: kernel BUG at mm/page_table_check.c:55! While it's pretty legal to use set_pxx_at() for ZONE_DEVICE pages for page fault resolutions, skip all the checks if page_ext doesn't even exist in pgtable checker, which applies to ZONE_DEVICE but maybe more. Link: https://lkml.kernel.org/r/20240605212146.994486-1-peterx@redhat.com Fixes: df4e817b7108 ("mm: page table check") Signed-off-by: Peter Xu Reviewed-by: Pasha Tatashin Reviewed-by: Dan Williams Reviewed-by: Alistair Popple Cc: Signed-off-by: Andrew Morton

mm/page_table_check: support userfault wr-protect entries

2024-05-06T00:53:41+00:00

Allow page_table_check hooks to check over userfaultfd wr-protect criteria upon pgtable updates. The rule is no co-existance allowed for any writable flag against userfault wr-protect flag. This should be better than c2da319c2e, where we used to only sanitize such issues during a pgtable walk, but when hitting such issue we don't have a good chance to know where does that writable bit came from [1], so that even the pgtable walk exposes a kernel bug (which is still helpful on triaging) but not easy to track and debug. Now we switch to track the source. It's much easier too with the recent introduction of page table check. There are some limitations with using the page table check here for userfaultfd wr-protect purpose: - It is only enabled with explicit enablement of page table check configs and/or boot parameters, but should be good enough to track at least syzbot issues, as syzbot should enable PAGE_TABLE_CHECK[_ENFORCED] for x86 [1]. We used to have DEBUG_VM but it's now off for most distros, while distros also normally not enable PAGE_TABLE_CHECK[_ENFORCED], which is similar. - It conditionally works with the ptep_modify_prot API. It will be bypassed when e.g. XEN PV is enabled, however still work for most of the rest scenarios, which should be the common cases so should be good enough. - Hugetlb check is a bit hairy, as the page table check cannot identify hugetlb pte or normal pte via trapping at set_pte_at(), because of the current design where hugetlb maps every layers to pte_t... For example, the default set_huge_pte_at() can invoke set_pte_at() directly and lose the hugetlb context, treating it the same as a normal pte_t. So far it's fine because we have huge_pte_uffd_wp() always equals to pte_uffd_wp() as long as supported (x86 only). It'll be a bigger problem when we'll define _PAGE_UFFD_WP differently at various pgtable levels, because then one huge_pte_uffd_wp() per-arch will stop making sense first.. as of now we can leave this for later too. This patch also removes commit c2da319c2e altogether, as we have something better now. [1] https://lore.kernel.org/all/000000000000dce0530615c89210@google.com/ Link: https://lkml.kernel.org/r/20240417212549.2766883-1-peterx@redhat.com Signed-off-by: Peter Xu Reviewed-by: Pasha Tatashin Cc: Axel Rasmussen Cc: David Hildenbrand Cc: Nadav Amit Signed-off-by: Andrew Morton

mm: convert page_table_check_pte_set() to page_table_check_ptes_set()

2023-08-24T23:20:18+00:00

Tell the page table check how many PTEs & PFNs we want it to check. Link: https://lkml.kernel.org/r/20230802151406.3735276-3-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Mike Rapoport (IBM) Acked-by: Pasha Tatashin Reviewed-by: Anshuman Khandual Signed-off-by: Andrew Morton

mm/page_ext: use page_ext_data helper in page_table_check

2023-08-21T20:37:27+00:00

Use page_ext_data helper in page_table_check to avoid access offset directly. Link: https://lkml.kernel.org/r/20230718145812.1991717-3-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Reviewed-by: Andrew Morton Acked-by: Mike Rapoport (IBM) Signed-off-by: Andrew Morton

mm/page_table_check: remove unused parameter in [__]page_table_check_pud_set

2023-08-18T17:12:29+00:00

Remove unused addr in __page_table_check_pud_set and page_table_check_pud_set. Link: https://lkml.kernel.org/r/20230713172636.1705415-9-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Cc: Pavel Tatashin Signed-off-by: Andrew Morton

mm/page_table_check: remove unused parameter in [__]page_table_check_pmd_set

2023-08-18T17:12:29+00:00

Remove unused addr in __page_table_check_pmd_set and page_table_check_pmd_set. Link: https://lkml.kernel.org/r/20230713172636.1705415-8-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Cc: Pavel Tatashin Signed-off-by: Andrew Morton

mm/page_table_check: remove unused parameter in [__]page_table_check_pte_set

2023-08-18T17:12:29+00:00

Remove unused addr in __page_table_check_pte_set and page_table_check_pte_set. Link: https://lkml.kernel.org/r/20230713172636.1705415-7-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Cc: Pavel Tatashin Signed-off-by: Andrew Morton

mm/page_table_check: remove unused parameter in [__]page_table_check_pud_clear

2023-08-18T17:12:28+00:00

Remove unused addr in __page_table_check_pud_clear and page_table_check_pud_clear. Link: https://lkml.kernel.org/r/20230713172636.1705415-6-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Cc: Pavel Tatashin Signed-off-by: Andrew Morton

mm/page_table_check: remove unused parameter in [__]page_table_check_pmd_clear

2023-08-18T17:12:28+00:00

Remove unused addr in page_table_check_pmd_clear and __page_table_check_pmd_clear. Link: https://lkml.kernel.org/r/20230713172636.1705415-5-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Cc: Pavel Tatashin Signed-off-by: Andrew Morton

mm/page_table_check: remove unused parameter in [__]page_table_check_pte_clear

2023-08-18T17:12:28+00:00

Remove unused addr in page_table_check_pte_clear and __page_table_check_pte_clear. Link: https://lkml.kernel.org/r/20230713172636.1705415-4-shikemeng@huaweicloud.com Signed-off-by: Kemeng Shi Cc: Pavel Tatashin Signed-off-by: Andrew Morton