user/sven/linux.git/mm/vmalloc.c, branch v6.6.26

mm: hugetlb: add huge page size param to set_huge_pte_at()

2023-09-30T00:20:47Z

Patch series "Fix set_huge_pte_at() panic on arm64", v2. This series fixes a bug in arm64's implementation of set_huge_pte_at(), which can result in an unprivileged user causing a kernel panic. The problem was triggered when running the new uffd poison mm selftest for HUGETLB memory. This test (and the uffd poison feature) was merged for v6.5-rc7. Ideally, I'd like to get this fix in for v6.6 and I've cc'ed stable (correctly this time) to get it backported to v6.5, where the issue first showed up. Description of Bug ================== arm64's huge pte implementation supports multiple huge page sizes, some of which are implemented in the page table with multiple contiguous entries. So set_huge_pte_at() needs to work out how big the logical pte is, so that it can also work out how many physical ptes (or pmds) need to be written. It previously did this by grabbing the folio out of the pte and querying its size. However, there are cases when the pte being set is actually a swap entry. But this also used to work fine, because for huge ptes, we only ever saw migration entries and hwpoison entries. And both of these types of swap entries have a PFN embedded, so the code would grab that and everything still worked out. But over time, more calls to set_huge_pte_at() have been added that set swap entry types that do not embed a PFN. And this causes the code to go bang. The triggering case is for the uffd poison test, commit 99aa77215ad0 ("selftests/mm: add uffd unit test for UFFDIO_POISON"), which causes a PTE_MARKER_POISONED swap entry to be set, coutesey of commit 8a13897fb0da ("mm: userfaultfd: support UFFDIO_POISON for hugetlbfs") - added in v6.5-rc7. Although review shows that there are other call sites that set PTE_MARKER_UFFD_WP (which also has no PFN), these don't trigger on arm64 because arm64 doesn't support UFFD WP. If CONFIG_DEBUG_VM is enabled, we do at least get a BUG(), but otherwise, it will dereference a bad pointer in page_folio(): static inline struct folio *hugetlb_swap_entry_to_folio(swp_entry_t entry) { VM_BUG_ON(!is_migration_entry(entry) && !is_hwpoison_entry(entry)); return page_folio(pfn_to_page(swp_offset_pfn(entry))); } Fix === The simplest fix would have been to revert the dodgy cleanup commit 18f3962953e4 ("mm: hugetlb: kill set_huge_swap_pte_at()"), but since things have moved on, this would have required an audit of all the new set_huge_pte_at() call sites to see if they should be converted to set_huge_swap_pte_at(). As per the original intent of the change, it would also leave us open to future bugs when people invariably get it wrong and call the wrong helper. So instead, I've added a huge page size parameter to set_huge_pte_at(). This means that the arm64 code has the size in all cases. It's a bigger change, due to needing to touch the arches that implement the function, but it is entirely mechanical, so in my view, low risk. I've compile-tested all touched arches; arm64, parisc, powerpc, riscv, s390, sparc (and additionally x86_64). I've additionally booted and run mm selftests against arm64, where I observe the uffd poison test is fixed, and there are no other regressions. This patch (of 2): In order to fix a bug, arm64 needs to be told the size of the huge page for which the pte is being set in set_huge_pte_at(). Provide for this by adding an `unsigned long sz` parameter to the function. This follows the same pattern as huge_pte_clear(). This commit makes the required interface modifications to the core mm as well as all arches that implement this function (arm64, parisc, powerpc, riscv, s390, sparc). The actual arm64 bug will be fixed in a separate commit. No behavioral changes intended. Link: https://lkml.kernel.org/r/20230922115804.2043771-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20230922115804.2043771-2-ryan.roberts@arm.com Fixes: 8a13897fb0da ("mm: userfaultfd: support UFFDIO_POISON for hugetlbfs") Signed-off-by: Ryan Roberts Reviewed-by: Christophe Leroy [powerpc 8xx] Reviewed-by: Lorenzo Stoakes [vmalloc change] Cc: Alexandre Ghiti Cc: Albert Ou Cc: Alexander Gordeev Cc: Anshuman Khandual Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Christoph Hellwig Cc: David S. Miller Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Helge Deller Cc: "James E.J. Bottomley" Cc: Mike Kravetz Cc: Muchun Song Cc: Nicholas Piggin Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Peter Xu Cc: Qi Zheng Cc: Ryan Roberts Cc: SeongJae Park Cc: Sven Schnelle Cc: Uladzislau Rezki (Sony) Cc: Vasily Gorbik Cc: Will Deacon Cc: [6.5+] Signed-off-by: Andrew Morton

mm/vmalloc: add a safer version of find_vm_area() for debug

2023-09-05T17:13:45Z

It is unsafe to dump vmalloc area information when trying to do so from some contexts. Add a safer trylock version of the same function to do a best-effort VMA finding and use it from vmalloc_dump_obj(). [applied test robot feedback on unused function fix.] [applied Uladzislau feedback on locking.] Link: https://lkml.kernel.org/r/20230904180806.1002832-1-joel@joelfernandes.org Fixes: 98f180837a89 ("mm: Make mem_dump_obj() handle vmalloc() memory") Signed-off-by: Joel Fernandes (Google) Reviewed-by: Uladzislau Rezki (Sony) Reported-by: Zhen Lei Cc: Paul E. McKenney Cc: Zqiang Cc: Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton

mm: add a call to flush_cache_vmap() in vmap_pfn()

2023-08-21T20:07:21Z

flush_cache_vmap() must be called after new vmalloc mappings are installed in the page table in order to allow architectures to make sure the new mapping is visible. It could lead to a panic since on some architectures (like powerpc), the page table walker could see the wrong pte value and trigger a spurious page fault that can not be resolved (see commit f1cb8f9beba8 ("powerpc/64s/radix: avoid ptesync after set_pte and ptep_set_access_flags")). But actually the patch is aiming at riscv: the riscv specification allows the caching of invalid entries in the TLB, and since we recently removed the vmalloc page fault handling, we now need to emit a tlb shootdown whenever a new vmalloc mapping is emitted (https://lore.kernel.org/linux-riscv/20230725132246.817726-1-alexghiti@rivosinc.com/). That's a temporary solution, there are ways to avoid that :) Link: https://lkml.kernel.org/r/20230809164633.1556126-1-alexghiti@rivosinc.com Fixes: 3e9a9e256b1e ("mm: add a vmap_pfn function") Reported-by: Dylan Jhong Closes: https://lore.kernel.org/linux-riscv/ZMytNY2J8iyjbPPy@atctrx.andestech.com/ Signed-off-by: Alexandre Ghiti Reviewed-by: Christoph Hellwig Reviewed-by: Palmer Dabbelt Acked-by: Palmer Dabbelt Reviewed-by: Dylan Jhong Cc: Signed-off-by: Andrew Morton

Merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes.

2023-06-23T23:58:19Z

mm: ptep_get() conversion

2023-06-19T23:19:25Z

Convert all instances of direct pte_t* dereferencing to instead use ptep_get() helper. This means that by default, the accesses change from a C dereference to a READ_ONCE(). This is technically the correct thing to do since where pgtables are modified by HW (for access/dirty) they are volatile and therefore we should always ensure READ_ONCE() semantics. But more importantly, by always using the helper, it can be overridden by the architecture to fully encapsulate the contents of the pte. Arch code is deliberately not converted, as the arch code knows best. It is intended that arch code (arm64) will override the default with its own implementation that can (e.g.) hide certain bits from the core code, or determine young/dirty status by mixing in state from another source. Conversion was done using Coccinelle: ---- // $ make coccicheck \ // COCCI=ptepget.cocci \ // SPFLAGS="--include-headers" \ // MODE=patch virtual patch @ depends on patch @ pte_t *v; @@ - *v + ptep_get(v) ---- Then reviewed and hand-edited to avoid multiple unnecessary calls to ptep_get(), instead opting to store the result of a single call in a variable, where it is correct to do so. This aims to negate any cost of READ_ONCE() and will benefit arch-overrides that may be more complex. Included is a fix for an issue in an earlier version of this patch that was pointed out by kernel test robot. The issue arose because config MMU=n elides definition of the ptep helper functions, including ptep_get(). HUGETLB_PAGE=n configs still define a simple huge_ptep_clear_flush() for linking purposes, which dereferences the ptep. So when both configs are disabled, this caused a build error because ptep_get() is not defined. Fix by continuing to do a direct dereference when MMU=n. This is safe because for this config the arch code cannot be trying to virtualize the ptes because none of the ptep helpers are defined. Link: https://lkml.kernel.org/r/20230612151545.3317766-4-ryan.roberts@arm.com Reported-by: kernel test robot Link: https://lore.kernel.org/oe-kbuild-all/202305120142.yXsNEo6H-lkp@intel.com/ Signed-off-by: Ryan Roberts Cc: Adrian Hunter Cc: Alexander Potapenko Cc: Alexander Shishkin Cc: Alex Williamson Cc: Al Viro Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Christian Brauner Cc: Christoph Hellwig Cc: Daniel Vetter Cc: Dave Airlie Cc: Dimitri Sivanich Cc: Dmitry Vyukov Cc: Ian Rogers Cc: Jason Gunthorpe Cc: Jérôme Glisse Cc: Jiri Olsa Cc: Johannes Weiner Cc: Kirill A. Shutemov Cc: Lorenzo Stoakes Cc: Mark Rutland Cc: Matthew Wilcox Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Kravetz Cc: Mike Rapoport (IBM) Cc: Muchun Song Cc: Namhyung Kim Cc: Naoya Horiguchi Cc: Oleksandr Tyshchenko Cc: Pavel Tatashin Cc: Roman Gushchin Cc: SeongJae Park Cc: Shakeel Butt Cc: Uladzislau Rezki (Sony) Cc: Vincenzo Frascino Cc: Yu Zhao Signed-off-by: Andrew Morton

mm/vmalloc: vmalloc_to_page() use pte_offset_kernel()

2023-06-19T23:19:14Z

vmalloc_to_page() was using pte_offset_map() (followed by pte_unmap()), but it's intended for userspace page tables: prefer pte_offset_kernel(). Link: https://lkml.kernel.org/r/696386a-84f8-b33c-82e5-f865ed6eb39@google.com Signed-off-by: Hugh Dickins Reviewed-by: Lorenzo Stoakes Cc: Alistair Popple Cc: Anshuman Khandual Cc: Axel Rasmussen Cc: Christophe Leroy Cc: Christoph Hellwig Cc: David Hildenbrand Cc: "Huang, Ying" Cc: Ira Weiny Cc: Jason Gunthorpe Cc: Kirill A. Shutemov Cc: Matthew Wilcox Cc: Mel Gorman Cc: Miaohe Lin Cc: Mike Kravetz Cc: Mike Rapoport (IBM) Cc: Minchan Kim Cc: Naoya Horiguchi Cc: Pavel Tatashin Cc: Peter Xu Cc: Peter Zijlstra Cc: Qi Zheng Cc: Ralph Campbell Cc: Ryan Roberts Cc: SeongJae Park Cc: Song Liu Cc: Steven Price Cc: Suren Baghdasaryan Cc: Thomas Hellström Cc: Will Deacon Cc: Yang Shi Cc: Yu Zhao Cc: Zack Rusin Signed-off-by: Andrew Morton

mm/vmalloc: replace the ternary conditional operator with min()

2023-06-19T23:19:11Z

It would be better to replace the traditional ternary conditional operator with min() in zero_iter Link: https://lkml.kernel.org/r/20230609093057.27777-1-luhongfei@vivo.com Signed-off-by: Lu Hongfei Reviewed-by: Lorenzo Stoakes Reviewed-by: David Hildenbrand Cc: Christoph Hellwig Cc: Uladzislau Rezki (Sony) Signed-off-by: Andrew Morton

mm/vmalloc: do not output a spurious warning when huge vmalloc() fails

2023-06-19T20:19:31Z

In __vmalloc_area_node() we always warn_alloc() when an allocation performed by vm_area_alloc_pages() fails unless it was due to a pending fatal signal. However, huge page allocations instigated either by vmalloc_huge() or __vmalloc_node_range() (or a caller that invokes this like kvmalloc() or kvmalloc_node()) always falls back to order-0 allocations if the huge page allocation fails. This renders the warning useless and noisy, especially as all callers appear to be aware that this may fallback. This has already resulted in at least one bug report from a user who was confused by this (see link). Therefore, simply update the code to only output this warning for order-0 pages when no fatal signal is pending. Link: https://bugzilla.suse.com/show_bug.cgi?id=1211410 Link: https://lkml.kernel.org/r/20230605201107.83298-1-lstoakes@gmail.com Fixes: 80b1d8fdfad1 ("mm: vmalloc: correct use of __GFP_NOWARN mask in __vmalloc_area_node()") Signed-off-by: Lorenzo Stoakes Acked-by: Vlastimil Babka Reviewed-by: Baoquan He Acked-by: Michal Hocko Reviewed-by: Uladzislau Rezki (Sony) Reviewed-by: David Hildenbrand Cc: Christoph Hellwig Cc: Signed-off-by: Andrew Morton

mm: vmalloc must set pte via arch code

2023-06-09T23:25:55Z

Patch series "Fixes for pte encapsulation bypasses", v3. A series to improve the encapsulation of pte entries by disallowing non-arch code from directly dereferencing pte_t pointers. This patch (of 4): It is bad practice to directly set pte entries within a pte table. Instead all modifications must go through arch-provided helpers such as set_pte_at() to give the arch code visibility and allow it to check (and potentially modify) the operation. Link: https://lkml.kernel.org/r/20230602092949.545577-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20230602092949.545577-2-ryan.roberts@arm.com Fixes: 3e9a9e256b1e ("mm: add a vmap_pfn function") Signed-off-by: Ryan Roberts Reviewed-by: Zi Yan Acked-by: Lorenzo Stoakes Reviewed-by: Christoph Hellwig Reviewed-by: Uladzislau Rezki (Sony) Reviewed-by: Mike Rapoport (IBM) Cc: Kirill A. Shutemov Cc: Matthew Wilcox (Oracle) Cc: SeongJae Park Cc: Yu Zhao Signed-off-by: Andrew Morton

mm/vmalloc: dont purge usable blocks unnecessarily

2023-06-09T23:25:41Z

Purging fragmented blocks is done unconditionally in several contexts: 1) From drain_vmap_area_work(), when the number of lazy to be freed vmap_areas reached the threshold 2) Reclaiming vmalloc address space from pcpu_get_vm_areas() 3) _vm_unmap_aliases() #1 There is no reason to zap fragmented vmap blocks unconditionally, simply because reclaiming all lazy areas drains at least 32MB * fls(num_online_cpus()) per invocation which is plenty. #2 Reclaiming when running out of space or due to memory pressure makes a lot of sense #3 _unmap_aliases() requires to touch everything because the caller has no clue which vmap_area used a particular page last and the vmap_area lost that information too. Except for the vfree + VM_FLUSH_RESET_PERMS case, which removes the vmap area first and then cares about the flush. That in turn requires a full walk of _all_ vmap areas including the one which was just added to the purge list. But as this has to be flushed anyway this is an opportunity to combine outstanding TLB flushes and do the housekeeping of purging freed areas, but like #1 there is no real good reason to zap usable vmap blocks unconditionally. Add a @force_purge argument to the newly split out block purge function and if not true only purge fragmented blocks which have less than 1/4 of their capacity left. Rename purge_vmap_area_lazy() to reclaim_and_purge_vmap_areas() to make it clear what the function does. [lstoakes@gmail.com: correct VMAP_PURGE_THRESHOLD check] Link: https://lkml.kernel.org/r/3e92ef61-b910-4576-88e7-cf43211fd4e7@lucifer.local Link: https://lkml.kernel.org/r/20230525124504.864005691@linutronix.de Signed-off-by: Thomas Gleixner Signed-off-by: Lorenzo Stoakes Reviewed-by: Baoquan He Cc: Christoph Hellwig Cc: Lorenzo Stoakes Cc: Uladzislau Rezki (Sony) Signed-off-by: Andrew Morton