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Gang Li 62c9827cbb shmem: fix a race between shmem_unused_huge_shrink and shmem_evict_inode
Fix a data race in commit 779750d20b ("shmem: split huge pages beyond
i_size under memory pressure").

Here are call traces causing race:

   Call Trace 1:
     shmem_unused_huge_shrink+0x3ae/0x410
     ? __list_lru_walk_one.isra.5+0x33/0x160
     super_cache_scan+0x17c/0x190
     shrink_slab.part.55+0x1ef/0x3f0
     shrink_node+0x10e/0x330
     kswapd+0x380/0x740
     kthread+0xfc/0x130
     ? mem_cgroup_shrink_node+0x170/0x170
     ? kthread_create_on_node+0x70/0x70
     ret_from_fork+0x1f/0x30

   Call Trace 2:
     shmem_evict_inode+0xd8/0x190
     evict+0xbe/0x1c0
     do_unlinkat+0x137/0x330
     do_syscall_64+0x76/0x120
     entry_SYSCALL_64_after_hwframe+0x3d/0xa2

A simple explanation:

Image there are 3 items in the local list (@list).  In the first
traversal, A is not deleted from @list.

  1)    A->B->C
        ^
        |
        pos (leave)

In the second traversal, B is deleted from @list.  Concurrently, A is
deleted from @list through shmem_evict_inode() since last reference
counter of inode is dropped by other thread.  Then the @list is corrupted.

  2)    A->B->C
        ^  ^
        |  |
     evict pos (drop)

We should make sure the inode is either on the global list or deleted from
any local list before iput().

Fixed by moving inodes back to global list before we put them.

[akpm@linux-foundation.org: coding style fixes]

Link: https://lkml.kernel.org/r/20211125064502.99983-1-ligang.bdlg@bytedance.com
Fixes: 779750d20b ("shmem: split huge pages beyond i_size under memory pressure")
Signed-off-by: Gang Li <ligang.bdlg@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-15 16:30:26 +02:00
arch mm: defer kmemleak object creation of module_alloc() 2022-01-15 16:30:25 +02:00
block block-5.16-2021-12-19 2021-12-19 12:38:53 -08:00
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Documentation mm/debug_vm_pgtable: update comments regarding migration swap entries 2022-01-15 16:30:26 +02:00
drivers device-dax: compound devmap support 2022-01-15 16:30:26 +02:00
fs mm,fs: split dump_mapping() out from dump_page() 2022-01-15 16:30:26 +02:00
include mm,fs: split dump_mapping() out from dump_page() 2022-01-15 16:30:26 +02:00
init kbuild: Fix -Wimplicit-fallthrough=5 error for GCC 5.x and 6.x 2021-11-14 18:59:49 -08:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-11-20 10:35:54 -08:00
kernel trace/hwlat: make use of the helper function kthread_run_on_cpu() 2022-01-15 16:30:24 +02:00
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LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm shmem: fix a race between shmem_unused_huge_shrink and shmem_evict_inode 2022-01-15 16:30:26 +02:00
net Two more changes: 2022-01-04 07:18:28 -08:00
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scripts scripts/spelling.txt: add "oveflow" 2022-01-15 16:30:24 +02:00
security selinux/stable-5.16 PR 20211228 2021-12-28 13:33:06 -08:00
sound sound fixes for 5.16-rc7 2021-12-23 09:55:58 -08:00
tools perf tools fixes for v5.16: 6th batch 2022-01-09 10:37:07 -08:00
usr initramfs: Check timestamp to prevent broken cpio archive 2021-10-24 13:48:40 +09:00
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Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
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Makefile Linux 5.16 2022-01-09 14:55:34 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.