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  1. 23 Mar, 2020 1 commit
  2. 22 Mar, 2020 12 commits
    • Linus Torvalds's avatar
      Merge tag 'for-5.6-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux · 67d584e3
      Linus Torvalds authored
      Pull btrfs fixes from David Sterba:
       "Two fixes.
      
        The first is a regression: when dropping some incompat bits the
        conditions were reversed. The other is a fix for rename whiteout
        potentially leaving stack memory linked to a list"
      
      * tag 'for-5.6-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
        btrfs: fix removal of raid[56|1c34} incompat flags after removing block group
        btrfs: fix log context list corruption after rename whiteout error
      67d584e3
    • Linus Torvalds's avatar
      Merge branch 'akpm' (patches from Andrew) · b3c03db6
      Linus Torvalds authored
      Merge misc fixes from Andrew Morton:
       "10 fixes"
      
      * emailed patches from Andrew Morton <akpm@linux-foundation.org>:
        x86/mm: split vmalloc_sync_all()
        mm, slub: prevent kmalloc_node crashes and memory leaks
        mm/mmu_notifier: silence PROVE_RCU_LIST warnings
        epoll: fix possible lost wakeup on epoll_ctl() path
        mm: do not allow MADV_PAGEOUT for CoW pages
        mm, memcg: throttle allocators based on ancestral memory.high
        mm, memcg: fix corruption on 64-bit divisor in memory.high throttling
        page-flags: fix a crash at SetPageError(THP_SWAP)
        mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case
        memcg: fix NULL pointer dereference in __mem_cgroup_usage_unregister_event
      b3c03db6
    • Joerg Roedel's avatar
      x86/mm: split vmalloc_sync_all() · 763802b5
      Joerg Roedel authored
      Commit 3f8fd02b ("mm/vmalloc: Sync unmappings in
      __purge_vmap_area_lazy()") introduced a call to vmalloc_sync_all() in
      the vunmap() code-path.  While this change was necessary to maintain
      correctness on x86-32-pae kernels, it also adds additional cycles for
      architectures that don't need it.
      
      Specifically on x86-64 with CONFIG_VMAP_STACK=y some people reported
      severe performance regressions in micro-benchmarks because it now also
      calls the x86-64 implementation of vmalloc_sync_all() on vunmap().  But
      the vmalloc_sync_all() implementation on x86-64 is only needed for newly
      created mappings.
      
      To avoid the unnecessary work on x86-64 and to gain the performance
      back, split up vmalloc_sync_all() into two functions:
      
      	* vmalloc_sync_mappings(), and
      	* vmalloc_sync_unmappings()
      
      Most call-sites to vmalloc_sync_all() only care about new mappings being
      synchronized.  The only exception is the new call-site added in the
      above mentioned commit.
      
      Shile Zhang directed us to a report of an 80% regression in reaim
      throughput.
      
      Fixes: 3f8fd02b ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()")
      Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
      Reported-by: default avatarShile Zhang <shile.zhang@linux.alibaba.com>
      Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Tested-by: default avatarBorislav Petkov <bp@suse.de>
      Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>	[GHES]
      Cc: Dave Hansen <dave.hansen@linux.intel.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: <stable@vger.kernel.org>
      Link: http://lkml.kernel.org/r/20191009124418.8286-1-joro@8bytes.org
      Link: https://lists.01.org/hyperkitty/list/lkp@lists.01.org/thread/4D3JPPHBNOSPFK2KEPC6KGKS6J25AIDB/
      Link: http://lkml.kernel.org/r/20191113095530.228959-1-shile.zhang@linux.alibaba.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      763802b5
    • Vlastimil Babka's avatar
      mm, slub: prevent kmalloc_node crashes and memory leaks · 0715e6c5
      Vlastimil Babka authored
      Sachin reports [1] a crash in SLUB __slab_alloc():
      
        BUG: Kernel NULL pointer dereference on read at 0x000073b0
        Faulting instruction address: 0xc0000000003d55f4
        Oops: Kernel access of bad area, sig: 11 [#1]
        LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
        Modules linked in:
        CPU: 19 PID: 1 Comm: systemd Not tainted 5.6.0-rc2-next-20200218-autotest #1
        NIP:  c0000000003d55f4 LR: c0000000003d5b94 CTR: 0000000000000000
        REGS: c0000008b37836d0 TRAP: 0300   Not tainted  (5.6.0-rc2-next-20200218-autotest)
        MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 24004844  XER: 00000000
        CFAR: c00000000000dec4 DAR: 00000000000073b0 DSISR: 40000000 IRQMASK: 1
        GPR00: c0000000003d5b94 c0000008b3783960 c00000000155d400 c0000008b301f500
        GPR04: 0000000000000dc0 0000000000000002 c0000000003443d8 c0000008bb398620
        GPR08: 00000008ba2f0000 0000000000000001 0000000000000000 0000000000000000
        GPR12: 0000000024004844 c00000001ec52a00 0000000000000000 0000000000000000
        GPR16: c0000008a1b20048 c000000001595898 c000000001750c18 0000000000000002
        GPR20: c000000001750c28 c000000001624470 0000000fffffffe0 5deadbeef0000122
        GPR24: 0000000000000001 0000000000000dc0 0000000000000002 c0000000003443d8
        GPR28: c0000008b301f500 c0000008bb398620 0000000000000000 c00c000002287180
        NIP ___slab_alloc+0x1f4/0x760
        LR __slab_alloc+0x34/0x60
        Call Trace:
          ___slab_alloc+0x334/0x760 (unreliable)
          __slab_alloc+0x34/0x60
          __kmalloc_node+0x110/0x490
          kvmalloc_node+0x58/0x110
          mem_cgroup_css_online+0x108/0x270
          online_css+0x48/0xd0
          cgroup_apply_control_enable+0x2ec/0x4d0
          cgroup_mkdir+0x228/0x5f0
          kernfs_iop_mkdir+0x90/0xf0
          vfs_mkdir+0x110/0x230
          do_mkdirat+0xb0/0x1a0
          system_call+0x5c/0x68
      
      This is a PowerPC platform with following NUMA topology:
      
        available: 2 nodes (0-1)
        node 0 cpus:
        node 0 size: 0 MB
        node 0 free: 0 MB
        node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
        node 1 size: 35247 MB
        node 1 free: 30907 MB
        node distances:
        node   0   1
          0:  10  40
          1:  40  10
      
        possible numa nodes: 0-31
      
      This only happens with a mmotm patch "mm/memcontrol.c: allocate
      shrinker_map on appropriate NUMA node" [2] which effectively calls
      kmalloc_node for each possible node.  SLUB however only allocates
      kmem_cache_node on online N_NORMAL_MEMORY nodes, and relies on
      node_to_mem_node to return such valid node for other nodes since commit
      a561ce00 ("slub: fall back to node_to_mem_node() node if allocating
      on memoryless node").  This is however not true in this configuration
      where the _node_numa_mem_ array is not initialized for nodes 0 and 2-31,
      thus it contains zeroes and get_partial() ends up accessing
      non-allocated kmem_cache_node.
      
      A related issue was reported by Bharata (originally by Ramachandran) [3]
      where a similar PowerPC configuration, but with mainline kernel without
      patch [2] ends up allocating large amounts of pages by kmalloc-1k
      kmalloc-512.  This seems to have the same underlying issue with
      node_to_mem_node() not behaving as expected, and might probably also
      lead to an infinite loop with CONFIG_SLUB_CPU_PARTIAL [4].
      
      This patch should fix both issues by not relying on node_to_mem_node()
      anymore and instead simply falling back to NUMA_NO_NODE, when
      kmalloc_node(node) is attempted for a node that's not online, or has no
      usable memory.  The "usable memory" condition is also changed from
      node_present_pages() to N_NORMAL_MEMORY node state, as that is exactly
      the condition that SLUB uses to allocate kmem_cache_node structures.
      The check in get_partial() is removed completely, as the checks in
      ___slab_alloc() are now sufficient to prevent get_partial() being
      reached with an invalid node.
      
      [1] https://lore.kernel.org/linux-next/3381CD91-AB3D-4773-BA04-E7A072A63968@linux.vnet.ibm.com/
      [2] https://lore.kernel.org/linux-mm/fff0e636-4c36-ed10-281c-8cdb0687c839@virtuozzo.com/
      [3] https://lore.kernel.org/linux-mm/20200317092624.GB22538@in.ibm.com/
      [4] https://lore.kernel.org/linux-mm/088b5996-faae-8a56-ef9c-5b567125ae54@suse.cz/
      
      Fixes: a561ce00 ("slub: fall back to node_to_mem_node() node if allocating on memoryless node")
      Reported-by: default avatarSachin Sant <sachinp@linux.vnet.ibm.com>
      Reported-by: default avatarPUVICHAKRAVARTHY RAMACHANDRAN <puvichakravarthy@in.ibm.com>
      Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Tested-by: default avatarSachin Sant <sachinp@linux.vnet.ibm.com>
      Tested-by: default avatarBharata B Rao <bharata@linux.ibm.com>
      Reviewed-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
      Cc: Mel Gorman <mgorman@techsingularity.net>
      Cc: Michael Ellerman <mpe@ellerman.id.au>
      Cc: Michal Hocko <mhocko@kernel.org>
      Cc: Christopher Lameter <cl@linux.com>
      Cc: linuxppc-dev@lists.ozlabs.org
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Cc: Nathan Lynch <nathanl@linux.ibm.com>
      Cc: <stable@vger.kernel.org>
      Link: http://lkml.kernel.org/r/20200320115533.9604-1-vbabka@suse.czDebugged-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0715e6c5
    • Qian Cai's avatar
      mm/mmu_notifier: silence PROVE_RCU_LIST warnings · 63886bad
      Qian Cai authored
      It is safe to traverse mm->notifier_subscriptions->list either under
      SRCU read lock or mm->notifier_subscriptions->lock using
      hlist_for_each_entry_rcu().  Silence the PROVE_RCU_LIST false positives,
      for example,
      
        WARNING: suspicious RCU usage
        -----------------------------
        mm/mmu_notifier.c:484 RCU-list traversed in non-reader section!!
      
        other info that might help us debug this:
      
        rcu_scheduler_active = 2, debug_locks = 1
        3 locks held by libvirtd/802:
         #0: ffff9321e3f58148 (&mm->mmap_sem#2){++++}, at: do_mprotect_pkey+0xe1/0x3e0
         #1: ffffffff91ae6160 (mmu_notifier_invalidate_range_start){+.+.}, at: change_p4d_range+0x5fa/0x800
         #2: ffffffff91ae6e08 (srcu){....}, at: __mmu_notifier_invalidate_range_start+0x178/0x460
      
        stack backtrace:
        CPU: 7 PID: 802 Comm: libvirtd Tainted: G          I       5.6.0-rc6-next-20200317+ #2
        Hardware name: HP ProLiant BL460c Gen8, BIOS I31 11/02/2014
        Call Trace:
          dump_stack+0xa4/0xfe
          lockdep_rcu_suspicious+0xeb/0xf5
          __mmu_notifier_invalidate_range_start+0x3ff/0x460
          change_p4d_range+0x746/0x800
          change_protection+0x1df/0x300
          mprotect_fixup+0x245/0x3e0
          do_mprotect_pkey+0x23b/0x3e0
          __x64_sys_mprotect+0x51/0x70
          do_syscall_64+0x91/0xae8
          entry_SYSCALL_64_after_hwframe+0x49/0xb3
      Signed-off-by: default avatarQian Cai <cai@lca.pw>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Reviewed-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      Reviewed-by: default avatarJason Gunthorpe <jgg@mellanox.com>
      Link: http://lkml.kernel.org/r/20200317175640.2047-1-cai@lca.pwSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      63886bad
    • Roman Penyaev's avatar
      epoll: fix possible lost wakeup on epoll_ctl() path · 1b53734b
      Roman Penyaev authored
      This fixes possible lost wakeup introduced by commit a218cc49.
      Originally modifications to ep->wq were serialized by ep->wq.lock, but
      in commit a218cc49 ("epoll: use rwlock in order to reduce
      ep_poll_callback() contention") a new rw lock was introduced in order to
      relax fd event path, i.e. callers of ep_poll_callback() function.
      
      After the change ep_modify and ep_insert (both are called on epoll_ctl()
      path) were switched to ep->lock, but ep_poll (epoll_wait) was using
      ep->wq.lock on wqueue list modification.
      
      The bug doesn't lead to any wqueue list corruptions, because wake up
      path and list modifications were serialized by ep->wq.lock internally,
      but actual waitqueue_active() check prior wake_up() call can be
      reordered with modifications of ep ready list, thus wake up can be lost.
      
      And yes, can be healed by explicit smp_mb():
      
        list_add_tail(&epi->rdlink, &ep->rdllist);
        smp_mb();
        if (waitqueue_active(&ep->wq))
      	wake_up(&ep->wp);
      
      But let's make it simple, thus current patch replaces ep->wq.lock with
      the ep->lock for wqueue modifications, thus wake up path always observes
      activeness of the wqueue correcty.
      
      Fixes: a218cc49 ("epoll: use rwlock in order to reduce ep_poll_callback() contention")
      Reported-by: default avatarMax Neunhoeffer <max@arangodb.com>
      Signed-off-by: default avatarRoman Penyaev <rpenyaev@suse.de>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Tested-by: default avatarMax Neunhoeffer <max@arangodb.com>
      Cc: Jakub Kicinski <kuba@kernel.org>
      Cc: Christopher Kohlhoff <chris.kohlhoff@clearpool.io>
      Cc: Davidlohr Bueso <dbueso@suse.de>
      Cc: Jason Baron <jbaron@akamai.com>
      Cc: Jes Sorensen <jes.sorensen@gmail.com>
      Cc: <stable@vger.kernel.org>	[5.1+]
      Link: http://lkml.kernel.org/r/20200214170211.561524-1-rpenyaev@suse.de
      References: https://bugzilla.kernel.org/show_bug.cgi?id=205933Bisected-by: default avatarMax Neunhoeffer <max@arangodb.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      1b53734b
    • Michal Hocko's avatar
      mm: do not allow MADV_PAGEOUT for CoW pages · 12e967fd
      Michal Hocko authored
      Jann has brought up a very interesting point [1].  While shared pages
      are excluded from MADV_PAGEOUT normally, CoW pages can be easily
      reclaimed that way.  This can lead to all sorts of hard to debug
      problems.  E.g.  performance problems outlined by Daniel [2].
      
      There are runtime environments where there is a substantial memory
      shared among security domains via CoW memory and a easy to reclaim way
      of that memory, which MADV_{COLD,PAGEOUT} offers, can lead to either
      performance degradation in for the parent process which might be more
      privileged or even open side channel attacks.
      
      The feasibility of the latter is not really clear to me TBH but there is
      no real reason for exposure at this stage.  It seems there is no real
      use case to depend on reclaiming CoW memory via madvise at this stage so
      it is much easier to simply disallow it and this is what this patch
      does.  Put it simply MADV_{PAGEOUT,COLD} can operate only on the
      exclusively owned memory which is a straightforward semantic.
      
      [1] http://lkml.kernel.org/r/CAG48ez0G3JkMq61gUmyQAaCq=_TwHbi1XKzWRooxZkv08PQKuw@mail.gmail.com
      [2] http://lkml.kernel.org/r/CAKOZueua_v8jHCpmEtTB6f3i9e2YnmX4mqdYVWhV4E=Z-n+zRQ@mail.gmail.com
      
      Fixes: 9c276cc6 ("mm: introduce MADV_COLD")
      Reported-by: default avatarJann Horn <jannh@google.com>
      Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Daniel Colascione <dancol@google.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>
      Cc: <stable@vger.kernel.org>
      Link: http://lkml.kernel.org/r/20200312082248.GS23944@dhcp22.suse.czSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      12e967fd
    • Chris Down's avatar
      mm, memcg: throttle allocators based on ancestral memory.high · e26733e0
      Chris Down authored
      Prior to this commit, we only directly check the affected cgroup's
      memory.high against its usage.  However, it's possible that we are being
      reclaimed as a result of hitting an ancestor memory.high and should be
      penalised based on that, instead.
      
      This patch changes memory.high overage throttling to use the largest
      overage in its ancestors when considering how many penalty jiffies to
      charge.  This makes sure that we penalise poorly behaving cgroups in the
      same way regardless of at what level of the hierarchy memory.high was
      breached.
      
      Fixes: 0e4b01df ("mm, memcg: throttle allocators when failing reclaim over memory.high")
      Reported-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: default avatarChris Down <chris@chrisdown.name>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Michal Hocko <mhocko@kernel.org>
      Cc: Nathan Chancellor <natechancellor@gmail.com>
      Cc: Roman Gushchin <guro@fb.com>
      Cc: <stable@vger.kernel.org>	[5.4.x+]
      Link: http://lkml.kernel.org/r/8cd132f84bd7e16cdb8fde3378cdbf05ba00d387.1584036142.git.chris@chrisdown.nameSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e26733e0
    • Chris Down's avatar
      mm, memcg: fix corruption on 64-bit divisor in memory.high throttling · d397a45f
      Chris Down authored
      Commit 0e4b01df had a bunch of fixups to use the right division
      method.  However, it seems that after all that it still wasn't right --
      div_u64 takes a 32-bit divisor.
      
      The headroom is still large (2^32 pages), so on mundane systems you
      won't hit this, but this should definitely be fixed.
      
      Fixes: 0e4b01df ("mm, memcg: throttle allocators when failing reclaim over memory.high")
      Reported-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Signed-off-by: default avatarChris Down <chris@chrisdown.name>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Roman Gushchin <guro@fb.com>
      Cc: Michal Hocko <mhocko@kernel.org>
      Cc: Nathan Chancellor <natechancellor@gmail.com>
      Cc: <stable@vger.kernel.org>	[5.4.x+]
      Link: http://lkml.kernel.org/r/80780887060514967d414b3cd91f9a316a16ab98.1584036142.git.chris@chrisdown.nameSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d397a45f
    • Qian Cai's avatar
      page-flags: fix a crash at SetPageError(THP_SWAP) · d72520ad
      Qian Cai authored
      Commit bd4c82c2 ("mm, THP, swap: delay splitting THP after swapped
      out") supported writing THP to a swap device but forgot to upgrade an
      older commit df8c94d1 ("page-flags: define behavior of FS/IO-related
      flags on compound pages") which could trigger a crash during THP
      swapping out with DEBUG_VM_PGFLAGS=y,
      
        kernel BUG at include/linux/page-flags.h:317!
      
        page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page))
        page:fffff3b2ec3a8000 refcount:512 mapcount:0 mapping:000000009eb0338c index:0x7f6e58200 head:fffff3b2ec3a8000 order:9 compound_mapcount:0 compound_pincount:0
        anon flags: 0x45fffe0000d8454(uptodate|lru|workingset|owner_priv_1|writeback|head|reclaim|swapbacked)
      
        end_swap_bio_write()
          SetPageError(page)
            VM_BUG_ON_PAGE(1 && PageCompound(page))
      
        <IRQ>
        bio_endio+0x297/0x560
        dec_pending+0x218/0x430 [dm_mod]
        clone_endio+0xe4/0x2c0 [dm_mod]
        bio_endio+0x297/0x560
        blk_update_request+0x201/0x920
        scsi_end_request+0x6b/0x4b0
        scsi_io_completion+0x509/0x7e0
        scsi_finish_command+0x1ed/0x2a0
        scsi_softirq_done+0x1c9/0x1d0
        __blk_mqnterrupt+0xf/0x20
        </IRQ>
      
      Fix by checking PF_NO_TAIL in those places instead.
      
      Fixes: bd4c82c2 ("mm, THP, swap: delay splitting THP after swapped out")
      Signed-off-by: default avatarQian Cai <cai@lca.pw>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
      Acked-by: default avatar"Huang, Ying" <ying.huang@intel.com>
      Acked-by: default avatarRafael Aquini <aquini@redhat.com>
      Cc: <stable@vger.kernel.org>
      Link: http://lkml.kernel.org/r/20200310235846.1319-1-cai@lca.pwSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d72520ad
    • Baoquan He's avatar
      mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case · d41e2f3b
      Baoquan He authored
      In section_deactivate(), pfn_to_page() doesn't work any more after
      ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case.  It
      causes a hot remove failure:
      
        kernel BUG at mm/page_alloc.c:4806!
        invalid opcode: 0000 [#1] SMP PTI
        CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G        W         5.5.0-next-20200205+ #340
        Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
        Workqueue: kacpi_hotplug acpi_hotplug_work_fn
        RIP: 0010:free_pages+0x85/0xa0
        Call Trace:
         __remove_pages+0x99/0xc0
         arch_remove_memory+0x23/0x4d
         try_remove_memory+0xc8/0x130
         __remove_memory+0xa/0x11
         acpi_memory_device_remove+0x72/0x100
         acpi_bus_trim+0x55/0x90
         acpi_device_hotplug+0x2eb/0x3d0
         acpi_hotplug_work_fn+0x1a/0x30
         process_one_work+0x1a7/0x370
         worker_thread+0x30/0x380
         kthread+0x112/0x130
         ret_from_fork+0x35/0x40
      
      Let's move the ->section_mem_map resetting after
      depopulate_section_memmap() to fix it.
      
      [akpm@linux-foundation.org: remove unneeded initialization, per David]
      Fixes: ba72b4c8 ("mm/sparsemem: support sub-section hotplug")
      Signed-off-by: default avatarBaoquan He <bhe@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Reviewed-by: default avatarPankaj Gupta <pankaj.gupta.linux@gmail.com>
      Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Cc: Wei Yang <richardw.yang@linux.intel.com>
      Cc: Oscar Salvador <osalvador@suse.de>
      Cc: Mike Rapoport <rppt@linux.ibm.com>
      Cc: <stable@vger.kernel.org>
      Link: http://lkml.kernel.org/r/20200307084229.28251-2-bhe@redhat.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d41e2f3b
    • Chunguang Xu's avatar
      memcg: fix NULL pointer dereference in __mem_cgroup_usage_unregister_event · 7d36665a
      Chunguang Xu authored
      An eventfd monitors multiple memory thresholds of the cgroup, closes them,
      the kernel deletes all events related to this eventfd.  Before all events
      are deleted, another eventfd monitors the memory threshold of this cgroup,
      leading to a crash:
      
        BUG: kernel NULL pointer dereference, address: 0000000000000004
        #PF: supervisor write access in kernel mode
        #PF: error_code(0x0002) - not-present page
        PGD 800000033058e067 P4D 800000033058e067 PUD 3355ce067 PMD 0
        Oops: 0002 [#1] SMP PTI
        CPU: 2 PID: 14012 Comm: kworker/2:6 Kdump: loaded Not tainted 5.6.0-rc4 #3
        Hardware name: LENOVO 20AWS01K00/20AWS01K00, BIOS GLET70WW (2.24 ) 05/21/2014
        Workqueue: events memcg_event_remove
        RIP: 0010:__mem_cgroup_usage_unregister_event+0xb3/0x190
        RSP: 0018:ffffb47e01c4fe18 EFLAGS: 00010202
        RAX: 0000000000000001 RBX: ffff8bb223a8a000 RCX: 0000000000000001
        RDX: 0000000000000001 RSI: ffff8bb22fb83540 RDI: 0000000000000001
        RBP: ffffb47e01c4fe48 R08: 0000000000000000 R09: 0000000000000010
        R10: 000000000000000c R11: 071c71c71c71c71c R12: ffff8bb226aba880
        R13: ffff8bb223a8a480 R14: 0000000000000000 R15: 0000000000000000
        FS:  0000000000000000(0000) GS:ffff8bb242680000(0000) knlGS:0000000000000000
        CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
        CR2: 0000000000000004 CR3: 000000032c29c003 CR4: 00000000001606e0
        Call Trace:
          memcg_event_remove+0x32/0x90
          process_one_work+0x172/0x380
          worker_thread+0x49/0x3f0
          kthread+0xf8/0x130
          ret_from_fork+0x35/0x40
        CR2: 0000000000000004
      
      We can reproduce this problem in the following ways:
      
      1. We create a new cgroup subdirectory and a new eventfd, and then we
         monitor multiple memory thresholds of the cgroup through this eventfd.
      
      2.  closing this eventfd, and __mem_cgroup_usage_unregister_event ()
         will be called multiple times to delete all events related to this
         eventfd.
      
      The first time __mem_cgroup_usage_unregister_event() is called, the
      kernel will clear all items related to this eventfd in thresholds->
      primary.
      
      Since there is currently only one eventfd, thresholds-> primary becomes
      empty, so the kernel will set thresholds-> primary and hresholds-> spare
      to NULL.  If at this time, the user creates a new eventfd and monitor
      the memory threshold of this cgroup, kernel will re-initialize
      thresholds-> primary.
      
      Then when __mem_cgroup_usage_unregister_event () is called for the
      second time, because thresholds-> primary is not empty, the system will
      access thresholds-> spare, but thresholds-> spare is NULL, which will
      trigger a crash.
      
      In general, the longer it takes to delete all events related to this
      eventfd, the easier it is to trigger this problem.
      
      The solution is to check whether the thresholds associated with the
      eventfd has been cleared when deleting the event.  If so, we do nothing.
      
      [akpm@linux-foundation.org: fix comment, per Kirill]
      Fixes: 907860ed ("cgroups: make cftype.unregister_event() void-returning")
      Signed-off-by: default avatarChunguang Xu <brookxu@tencent.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
      Cc: <stable@vger.kernel.org>
      Link: http://lkml.kernel.org/r/077a6f67-aefa-4591-efec-f2f3af2b0b02@gmail.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7d36665a
  3. 21 Mar, 2020 7 commits
  4. 20 Mar, 2020 20 commits