kernel/git/stable/linux.git/mm, branch linux-5.14.y

mm, oom: do not trigger out_of_memory from the #PF

2021-11-17T10:04:47+00:00

commit 60e2793d440a3ec95abb5d6d4fc034a4b480472d upstream. Any allocation failure during the #PF path will return with VM_FAULT_OOM which in turn results in pagefault_out_of_memory. This can happen for 2 different reasons. a) Memcg is out of memory and we rely on mem_cgroup_oom_synchronize to perform the memcg OOM handling or b) normal allocation fails. The latter is quite problematic because allocation paths already trigger out_of_memory and the page allocator tries really hard to not fail allocations. Anyway, if the OOM killer has been already invoked there is no reason to invoke it again from the #PF path. Especially when the OOM condition might be gone by that time and we have no way to find out other than allocate. Moreover if the allocation failed and the OOM killer hasn't been invoked then we are unlikely to do the right thing from the #PF context because we have already lost the allocation context and restictions and therefore might oom kill a task from a different NUMA domain. This all suggests that there is no legitimate reason to trigger out_of_memory from pagefault_out_of_memory so drop it. Just to be sure that no #PF path returns with VM_FAULT_OOM without allocation print a warning that this is happening before we restart the #PF. [VvS: #PF allocation can hit into limit of cgroup v1 kmem controller. This is a local problem related to memcg, however, it causes unnecessary global OOM kills that are repeated over and over again and escalate into a real disaster. This has been broken since kmem accounting has been introduced for cgroup v1 (3.8). There was no kmem specific reclaim for the separate limit so the only way to handle kmem hard limit was to return with ENOMEM. In upstream the problem will be fixed by removing the outdated kmem limit, however stable and LTS kernels cannot do it and are still affected. This patch fixes the problem and should be backported into stable/LTS.] Link: https://lkml.kernel.org/r/f5fd8dd8-0ad4-c524-5f65-920b01972a42@virtuozzo.com Signed-off-by: Michal Hocko Signed-off-by: Vasily Averin Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Mel Gorman Cc: Roman Gushchin Cc: Shakeel Butt Cc: Tetsuo Handa Cc: Uladzislau Rezki Cc: Vladimir Davydov Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm, oom: pagefault_out_of_memory: don't force global OOM for dying tasks

2021-11-17T10:04:47+00:00

commit 0b28179a6138a5edd9d82ad2687c05b3773c387b upstream. Patch series "memcg: prohibit unconditional exceeding the limit of dying tasks", v3. Memory cgroup charging allows killed or exiting tasks to exceed the hard limit. It can be misused and allowed to trigger global OOM from inside a memcg-limited container. On the other hand if memcg fails allocation, called from inside #PF handler it triggers global OOM from inside pagefault_out_of_memory(). To prevent these problems this patchset: (a) removes execution of out_of_memory() from pagefault_out_of_memory(), becasue nobody can explain why it is necessary. (b) allow memcg to fail allocation of dying/killed tasks. This patch (of 3): Any allocation failure during the #PF path will return with VM_FAULT_OOM which in turn results in pagefault_out_of_memory which in turn executes out_out_memory() and can kill a random task. An allocation might fail when the current task is the oom victim and there are no memory reserves left. The OOM killer is already handled at the page allocator level for the global OOM and at the charging level for the memcg one. Both have much more information about the scope of allocation/charge request. This means that either the OOM killer has been invoked properly and didn't lead to the allocation success or it has been skipped because it couldn't have been invoked. In both cases triggering it from here is pointless and even harmful. It makes much more sense to let the killed task die rather than to wake up an eternally hungry oom-killer and send him to choose a fatter victim for breakfast. Link: https://lkml.kernel.org/r/0828a149-786e-7c06-b70a-52d086818ea3@virtuozzo.com Signed-off-by: Vasily Averin Suggested-by: Michal Hocko Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Mel Gorman Cc: Roman Gushchin Cc: Shakeel Butt Cc: Tetsuo Handa Cc: Uladzislau Rezki Cc: Vladimir Davydov Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

memcg: prohibit unconditional exceeding the limit of dying tasks

2021-11-17T10:04:47+00:00

commit a4ebf1b6ca1e011289677239a2a361fde4a88076 upstream. Memory cgroup charging allows killed or exiting tasks to exceed the hard limit. It is assumed that the amount of the memory charged by those tasks is bound and most of the memory will get released while the task is exiting. This is resembling a heuristic for the global OOM situation when tasks get access to memory reserves. There is no global memory shortage at the memcg level so the memcg heuristic is more relieved. The above assumption is overly optimistic though. E.g. vmalloc can scale to really large requests and the heuristic would allow that. We used to have an early break in the vmalloc allocator for killed tasks but this has been reverted by commit b8c8a338f75e ("Revert "vmalloc: back off when the current task is killed""). There are likely other similar code paths which do not check for fatal signals in an allocation&charge loop. Also there are some kernel objects charged to a memcg which are not bound to a process life time. It has been observed that it is not really hard to trigger these bypasses and cause global OOM situation. One potential way to address these runaways would be to limit the amount of excess (similar to the global OOM with limited oom reserves). This is certainly possible but it is not really clear how much of an excess is desirable and still protects from global OOMs as that would have to consider the overall memcg configuration. This patch is addressing the problem by removing the heuristic altogether. Bypass is only allowed for requests which either cannot fail or where the failure is not desirable while excess should be still limited (e.g. atomic requests). Implementation wise a killed or dying task fails to charge if it has passed the OOM killer stage. That should give all forms of reclaim chance to restore the limit before the failure (ENOMEM) and tell the caller to back off. In addition, this patch renames should_force_charge() helper to task_is_dying() because now its use is not associated witch forced charging. This patch depends on pagefault_out_of_memory() to not trigger out_of_memory(), because then a memcg failure can unwind to VM_FAULT_OOM and cause a global OOM killer. Link: https://lkml.kernel.org/r/8f5cebbb-06da-4902-91f0-6566fc4b4203@virtuozzo.com Signed-off-by: Vasily Averin Suggested-by: Michal Hocko Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Cc: Roman Gushchin Cc: Uladzislau Rezki Cc: Vlastimil Babka Cc: Shakeel Butt Cc: Mel Gorman Cc: Tetsuo Handa Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm/filemap.c: remove bogus VM_BUG_ON

2021-11-17T10:04:47+00:00

commit d417b49fff3e2f21043c834841e8623a6098741d upstream. It is not safe to check page->index without holding the page lock. It can be changed if the page is moved between the swap cache and the page cache for a shmem file, for example. There is a VM_BUG_ON below which checks page->index is correct after taking the page lock. Link: https://lkml.kernel.org/r/20210818144932.940640-1-willy@infradead.org Fixes: 5c211ba29deb ("mm: add and use find_lock_entries") Signed-off-by: Matthew Wilcox (Oracle) Reported-by: Cc: Hugh Dickins Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm/zsmalloc.c: close race window between zs_pool_dec_isolated() and zs_unregister_migration()

2021-11-17T10:04:41+00:00

[ Upstream commit afe8605ca45424629fdddfd85984b442c763dc47 ] There is one possible race window between zs_pool_dec_isolated() and zs_unregister_migration() because wait_for_isolated_drain() checks the isolated count without holding class->lock and there is no order inside zs_pool_dec_isolated(). Thus the below race window could be possible: zs_pool_dec_isolated zs_unregister_migration check pool->destroying != 0 pool->destroying = true; smp_mb(); wait_for_isolated_drain() wait for pool->isolated_pages == 0 atomic_long_dec(&pool->isolated_pages); atomic_long_read(&pool->isolated_pages) == 0 Since we observe the pool->destroying (false) before atomic_long_dec() for pool->isolated_pages, waking pool->migration_wait up is missed. Fix this by ensure checking pool->destroying happens after the atomic_long_dec(&pool->isolated_pages). Link: https://lkml.kernel.org/r/20210708115027.7557-1-linmiaohe@huawei.com Fixes: 701d678599d0 ("mm/zsmalloc.c: fix race condition in zs_destroy_pool") Signed-off-by: Miaohe Lin Cc: Minchan Kim Cc: Sergey Senozhatsky Cc: Henry Burns Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

mm: khugepaged: skip huge page collapse for special files

2021-11-02T18:50:53+00:00

commit a4aeaa06d45e90f9b279f0b09de84bd00006e733 upstream. The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [shy828301@gmail.com: fix vm_file check [3]] Link: https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@mail.gmail.com/ [1] Link: https://lore.kernel.org/linux-mm/000000000000c6a82505ce284e4c@google.com/ [2] Link: https://lkml.kernel.org/r/CAHbLzkqTW9U3VvTu1Ki5v_cLRC9gHW+znBukg_ycergE0JWj-A@mail.gmail.com [3] Link: https://lkml.kernel.org/r/20211027195221.3825-1-shy828301@gmail.com Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Hugh Dickins Signed-off-by: Yang Shi Reported-by: Hao Sun Reported-by: syzbot+aae069be1de40fb11825@syzkaller.appspotmail.com Cc: Matthew Wilcox Cc: Kirill A. Shutemov Cc: Song Liu Cc: Andrea Righi Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm, thp: bail out early in collapse_file for writeback page

2021-11-02T18:50:53+00:00

commit 74c42e1baacf206338b1dd6b6199ac964512b5bb upstream. Currently collapse_file does not explicitly check PG_writeback, instead, page_has_private and try_to_release_page are used to filter writeback pages. This does not work for xfs with blocksize equal to or larger than pagesize, because in such case xfs has no page->private. This makes collapse_file bail out early for writeback page. Otherwise, xfs end_page_writeback will panic as follows. page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:ffff0003f88c86a8 index:0x0 pfn:0x84ef32 aops:xfs_address_space_operations [xfs] ino:30000b7 dentry name:"libtest.so" flags: 0x57fffe0000008027(locked|referenced|uptodate|active|writeback) raw: 57fffe0000008027 ffff80001b48bc28 ffff80001b48bc28 ffff0003f88c86a8 raw: 0000000000000000 0000000000000000 00000000ffffffff ffff0000c3e9a000 page dumped because: VM_BUG_ON_PAGE(((unsigned int) page_ref_count(page) + 127u <= 127u)) page->mem_cgroup:ffff0000c3e9a000 ------------[ cut here ]------------ kernel BUG at include/linux/mm.h:1212! Internal error: Oops - BUG: 0 [#1] SMP Modules linked in: BUG: Bad page state in process khugepaged pfn:84ef32 xfs(E) page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:0 index:0x0 pfn:0x84ef32 libcrc32c(E) rfkill(E) aes_ce_blk(E) crypto_simd(E) ... CPU: 25 PID: 0 Comm: swapper/25 Kdump: loaded Tainted: ... pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--) Call trace: end_page_writeback+0x1c0/0x214 iomap_finish_page_writeback+0x13c/0x204 iomap_finish_ioend+0xe8/0x19c iomap_writepage_end_bio+0x38/0x50 bio_endio+0x168/0x1ec blk_update_request+0x278/0x3f0 blk_mq_end_request+0x34/0x15c virtblk_request_done+0x38/0x74 [virtio_blk] blk_done_softirq+0xc4/0x110 __do_softirq+0x128/0x38c __irq_exit_rcu+0x118/0x150 irq_exit+0x1c/0x30 __handle_domain_irq+0x8c/0xf0 gic_handle_irq+0x84/0x108 el1_irq+0xcc/0x180 arch_cpu_idle+0x18/0x40 default_idle_call+0x4c/0x1a0 cpuidle_idle_call+0x168/0x1e0 do_idle+0xb4/0x104 cpu_startup_entry+0x30/0x9c secondary_start_kernel+0x104/0x180 Code: d4210000 b0006161 910c8021 94013f4d (d4210000) ---[ end trace 4a88c6a074082f8c ]--- Kernel panic - not syncing: Oops - BUG: Fatal exception in interrupt Link: https://lkml.kernel.org/r/20211022023052.33114-1-rongwei.wang@linux.alibaba.com Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Rongwei Wang Signed-off-by: Xu Yu Suggested-by: Yang Shi Reviewed-by: Matthew Wilcox (Oracle) Reviewed-by: Yang Shi Acked-by: Kirill A. Shutemov Cc: Song Liu Cc: William Kucharski Cc: Hugh Dickins Cc: Mike Kravetz Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: filemap: check if THP has hwpoisoned subpage for PMD page fault

2021-11-02T18:50:53+00:00

commit eac96c3efdb593df1a57bb5b95dbe037bfa9a522 upstream. 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 after the refcount is bumped successfully, then cleared when the THP is freed or split. The soft offline path doesn't need this since soft offline handler just marks a subpage hwpoisoned when the subpage is migrated successfully. But shmem THP didn't get split then migrated at all. Link: https://lkml.kernel.org/r/20211020210755.23964-3-shy828301@gmail.com Fixes: 800d8c63b2e9 ("shmem: add huge pages support") Signed-off-by: Yang Shi Reviewed-by: Naoya Horiguchi Suggested-by: Kirill A. Shutemov Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Oscar Salvador Cc: Peter Xu Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: hwpoison: remove the unnecessary THP check

2021-11-02T18:50:53+00:00

commit c7cb42e94473aafe553c0f2a3d8ca904599399ed upstream. When handling THP hwpoison checked if the THP is in allocation or free stage since hwpoison may mistreat it as hugetlb page. After commit 415c64c1453a ("mm/memory-failure: split thp earlier in memory error handling") the problem has been fixed, so this check is no longer needed. Remove it. The side effect of the removal is hwpoison may report unsplit THP instead of unknown error for shmem THP. It seems not like a big deal. The following patch "mm: filemap: check if THP has hwpoisoned subpage for PMD page fault" depends on this, which fixes shmem THP with hwpoisoned subpage(s) are mapped PMD wrongly. So this patch needs to be backported to -stable as well. Link: https://lkml.kernel.org/r/20211020210755.23964-2-shy828301@gmail.com Signed-off-by: Yang Shi Suggested-by: Naoya Horiguchi Acked-by: Naoya Horiguchi Cc: Hugh Dickins Cc: Kirill A. Shutemov Cc: Matthew Wilcox Cc: Oscar Salvador Cc: Peter Xu Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm/thp: decrease nr_thps in file's mapping on THP split

2021-10-27T07:59:53+00:00

[ Upstream commit 1ca7554d05ac038c98271f8968ed821266ecaa9c ] Decrease nr_thps counter in file's mapping to ensure that the page cache won't be dropped excessively on file write access if page has been already split. I've tried a test scenario running a big binary, kernel remaps it with THPs, then force a THP split with /sys/kernel/debug/split_huge_pages. During any further open of that binary with O_RDWR or O_WRITEONLY kernel drops page cache for it, because of non-zero thps counter. Link: https://lkml.kernel.org/r/20211012120237.2600-1-m.szyprowski@samsung.com Signed-off-by: Marek Szyprowski Fixes: 09d91cda0e82 ("mm,thp: avoid writes to file with THP in pagecache") Fixes: 06d3eff62d9d ("mm/thp: fix node page state in split_huge_page_to_list()") Acked-by: Matthew Wilcox (Oracle) Reviewed-by: Yang Shi Cc: Cc: Song Liu Cc: Rik van Riel Cc: "Kirill A . Shutemov" Cc: Johannes Weiner Cc: Hillf Danton Cc: Hugh Dickins Cc: William Kucharski Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin