linux/mm, branch v5.8

khugepaged: fix null-pointer dereference due to race

2020-07-24T19:42:41Z

khugepaged has to drop mmap lock several times while collapsing a page. The situation can change while the lock is dropped and we need to re-validate that the VMA is still in place and the PMD is still subject for collapse. But we miss one corner case: while collapsing an anonymous pages the VMA could be replaced with file VMA. If the file VMA doesn't have any private pages we get NULL pointer dereference: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] anon_vma_lock_write include/linux/rmap.h:120 [inline] collapse_huge_page mm/khugepaged.c:1110 [inline] khugepaged_scan_pmd mm/khugepaged.c:1349 [inline] khugepaged_scan_mm_slot mm/khugepaged.c:2110 [inline] khugepaged_do_scan mm/khugepaged.c:2193 [inline] khugepaged+0x3bba/0x5a10 mm/khugepaged.c:2238 The fix is to make sure that the VMA is anonymous in hugepage_vma_revalidate(). The helper is only used for collapsing anonymous pages. Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Reported-by: syzbot+ed318e8b790ca72c5ad0@syzkaller.appspotmail.com Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Reviewed-by: David Hildenbrand Acked-by: Yang Shi Cc: Link: http://lkml.kernel.org/r/20200722121439.44328-1-kirill.shutemov@linux.intel.com Signed-off-by: Linus Torvalds

mm/hugetlb: avoid hardcoding while checking if cma is enabled

2020-07-24T19:42:41Z

hugetlb_cma[0] can be NULL due to various reasons, for example, node0 has no memory. so NULL hugetlb_cma[0] doesn't necessarily mean cma is not enabled. gigantic pages might have been reserved on other nodes. This patch fixes possible double reservation and CMA leak. [akpm@linux-foundation.org: fix CONFIG_CMA=n warning] [sfr@canb.auug.org.au: better checks before using hugetlb_cma] Link: http://lkml.kernel.org/r/20200721205716.6dbaa56b@canb.auug.org.au Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma") Signed-off-by: Barry Song Signed-off-by: Andrew Morton Reviewed-by: Mike Kravetz Acked-by: Roman Gushchin Cc: Jonathan Cameron Cc: Link: http://lkml.kernel.org/r/20200710005726.36068-1-song.bao.hua@hisilicon.com Signed-off-by: Linus Torvalds

mm: memcg/slab: fix memory leak at non-root kmem_cache destroy

2020-07-24T19:42:41Z

If the kmem_cache refcount is greater than one, we should not mark the root kmem_cache as dying. If we mark the root kmem_cache dying incorrectly, the non-root kmem_cache can never be destroyed. It resulted in memory leak when memcg was destroyed. We can use the following steps to reproduce. 1) Use kmem_cache_create() to create a new kmem_cache named A. 2) Coincidentally, the kmem_cache A is an alias for kmem_cache B, so the refcount of B is just increased. 3) Use kmem_cache_destroy() to destroy the kmem_cache A, just decrease the B's refcount but mark the B as dying. 4) Create a new memory cgroup and alloc memory from the kmem_cache B. It leads to create a non-root kmem_cache for allocating memory. 5) When destroy the memory cgroup created in the step 4), the non-root kmem_cache can never be destroyed. If we repeat steps 4) and 5), this will cause a lot of memory leak. So only when refcount reach zero, we mark the root kmem_cache as dying. Fixes: 92ee383f6daa ("mm: fix race between kmem_cache destroy, create and deactivate") Signed-off-by: Muchun Song Signed-off-by: Andrew Morton Reviewed-by: Shakeel Butt Acked-by: Roman Gushchin Cc: Vlastimil Babka Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Shakeel Butt Cc: Link: http://lkml.kernel.org/r/20200716165103.83462-1-songmuchun@bytedance.com Signed-off-by: Linus Torvalds

mm/memcg: fix refcount error while moving and swapping

2020-07-24T19:42:41Z

It was hard to keep a test running, moving tasks between memcgs with move_charge_at_immigrate, while swapping: mem_cgroup_id_get_many()'s refcount is discovered to be 0 (supposedly impossible), so it is then forced to REFCOUNT_SATURATED, and after thousands of warnings in quick succession, the test is at last put out of misery by being OOM killed. This is because of the way moved_swap accounting was saved up until the task move gets completed in __mem_cgroup_clear_mc(), deferred from when mem_cgroup_move_swap_account() actually exchanged old and new ids. Concurrent activity can free up swap quicker than the task is scanned, bringing id refcount down 0 (which should only be possible when offlining). Just skip that optimization: do that part of the accounting immediately. Fixes: 615d66c37c75 ("mm: memcontrol: fix memcg id ref counter on swap charge move") Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Reviewed-by: Alex Shi Cc: Johannes Weiner Cc: Alex Shi Cc: Shakeel Butt Cc: Michal Hocko Cc: Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2007071431050.4726@eggly.anvils Signed-off-by: Linus Torvalds

mm/memcontrol: fix OOPS inside mem_cgroup_get_nr_swap_pages()

2020-07-24T19:42:41Z

Prabhakar reported an OOPS inside mem_cgroup_get_nr_swap_pages() function in a corner case seen on some arm64 boards when kdump kernel runs with "cgroup_disable=memory" passed to the kdump kernel via bootargs. The root-cause behind the same is that currently mem_cgroup_swap_init() function is implemented as a subsys_initcall() call instead of a core_initcall(), this means 'cgroup_memory_noswap' still remains set to the default value (false) even when memcg is disabled via "cgroup_disable=memory" boot parameter. This may result in premature OOPS inside mem_cgroup_get_nr_swap_pages() function in corner cases: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000188 Mem abort info: ESR = 0x96000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 [0000000000000188] user address but active_mm is swapper Internal error: Oops: 96000006 [#1] SMP Modules linked in: <..snip..> Call trace: mem_cgroup_get_nr_swap_pages+0x9c/0xf4 shrink_lruvec+0x404/0x4f8 shrink_node+0x1a8/0x688 do_try_to_free_pages+0xe8/0x448 try_to_free_pages+0x110/0x230 __alloc_pages_slowpath.constprop.106+0x2b8/0xb48 __alloc_pages_nodemask+0x2ac/0x2f8 alloc_page_interleave+0x20/0x90 alloc_pages_current+0xdc/0xf8 atomic_pool_expand+0x60/0x210 __dma_atomic_pool_init+0x50/0xa4 dma_atomic_pool_init+0xac/0x158 do_one_initcall+0x50/0x218 kernel_init_freeable+0x22c/0x2d0 kernel_init+0x18/0x110 ret_from_fork+0x10/0x18 Code: aa1403e3 91106000 97f82a27 14000011 (f940c663) ---[ end trace 9795948475817de4 ]--- Kernel panic - not syncing: Fatal exception Rebooting in 10 seconds.. Fixes: eccb52e78809 ("mm: memcontrol: prepare swap controller setup for integration") Reported-by: Prabhakar Kushwaha Signed-off-by: Bhupesh Sharma Signed-off-by: Andrew Morton Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Vladimir Davydov Cc: James Morse Cc: Mark Rutland Cc: Will Deacon Cc: Catalin Marinas Link: http://lkml.kernel.org/r/1593641660-13254-2-git-send-email-bhsharma@redhat.com Signed-off-by: Linus Torvalds

mm: initialize return of vm_insert_pages

2020-07-24T19:42:41Z

clang static analysis reports a garbage return In file included from mm/memory.c:84: mm/memory.c:1612:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn] return err; ^~~~~~~~~~ The setting of err depends on a loop executing. So initialize err. Signed-off-by: Tom Rix Signed-off-by: Andrew Morton Link: http://lkml.kernel.org/r/20200703155354.29132-1-trix@redhat.com Signed-off-by: Linus Torvalds

vfs/xattr: mm/shmem: kernfs: release simple xattr entry in a right way

2020-07-24T19:42:41Z

After commit fdc85222d58e ("kernfs: kvmalloc xattr value instead of kmalloc"), simple xattr entry is allocated with kvmalloc() instead of kmalloc(), so we should release it with kvfree() instead of kfree(). Fixes: fdc85222d58e ("kernfs: kvmalloc xattr value instead of kmalloc") Signed-off-by: Chengguang Xu Signed-off-by: Andrew Morton Acked-by: Hugh Dickins Acked-by: Tejun Heo Cc: Daniel Xu Cc: Chris Down Cc: Andreas Dilger Cc: Greg Kroah-Hartman Cc: Al Viro Cc: [5.7] Link: http://lkml.kernel.org/r/20200704051608.15043-1-cgxu519@mykernel.net Signed-off-by: Linus Torvalds

mm/mmap.c: close race between munmap() and expand_upwards()/downwards()

2020-07-24T19:42:41Z

VMA with VM_GROWSDOWN or VM_GROWSUP flag set can change their size under mmap_read_lock(). It can lead to race with __do_munmap(): Thread A Thread B __do_munmap() detach_vmas_to_be_unmapped() mmap_write_downgrade() expand_downwards() vma->vm_start = address; // The VMA now overlaps with // VMAs detached by the Thread A // page fault populates expanded part // of the VMA unmap_region() // Zaps pagetables partly // populated by Thread B Similar race exists for expand_upwards(). The fix is to avoid downgrading mmap_lock in __do_munmap() if detached VMAs are next to VM_GROWSDOWN or VM_GROWSUP VMA. [akpm@linux-foundation.org: s/mmap_sem/mmap_lock/ in comment] Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") Reported-by: Jann Horn Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Reviewed-by: Yang Shi Acked-by: Vlastimil Babka Cc: Oleg Nesterov Cc: Matthew Wilcox Cc: [4.20+] Link: http://lkml.kernel.org/r/20200709105309.42495-1-kirill.shutemov@linux.intel.com Signed-off-by: Linus Torvalds

mm: document warning in move_normal_pmd() and make it warn only once

2020-07-13T18:37:39Z

Naresh Kamboju reported that the LTP tests can cause warnings on i386 going back all the way to v5.0, and bisected it to commit 2c91bd4a4e2e ("mm: speed up mremap by 20x on large regions"). The warning in move_normal_pmd() is actually mostly correct, but we have a very unusual special case at process creation time, when we may move the stack down with an overlapping mode (kind of like a "memmove()" except using the page tables). And when you have just the right condition of "move a large initial stack by the right alignment in the end, but with the early part of the move being only page-aligned", we'll be in a situation where we're trying to move a normal PMD entry on top of an already existing - but now empty - PMD entry. The warning is still worth having, in case it ever triggers other cases, and perhaps as a reminder that we could do the stack move case more efficiently (although it's clearly rare enough that it probably doesn't matter). But make it do WARN_ON_ONCE(), so that you can't flood the logs with it. And add a *big* comment above it to explain and remind us what's going on, because it took some figuring out to see how this could trigger. Kudos to Joel Fernandes for debugging this. Reported-by: Naresh Kamboju Debugged-and-acked-by: Joel Fernandes Cc: Arnd Bergmann Cc: Kirill A. Shutemov Signed-off-by: Linus Torvalds

Merge tag 'gfs2-v5.8-rc4.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2

2020-07-10T15:53:21Z

Pull gfs2 fixes from Andreas Gruenbacher: "Fix gfs2 readahead deadlocks by adding a IOCB_NOIO flag that allows gfs2 to use the generic fiel read iterator functions without having to worry about being called back while holding locks". * tag 'gfs2-v5.8-rc4.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2: gfs2: Rework read and page fault locking fs: Add IOCB_NOIO flag for generic_file_read_iter