1. 26 Sep, 2019 1 commit
    • Michal Hocko's avatar
      memcg, kmem: do not fail __GFP_NOFAIL charges · e55d9d9b
      Michal Hocko authored
      Thomas has noticed the following NULL ptr dereference when using cgroup
      v1 kmem limit:
      BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
      PGD 0
      P4D 0
      Oops: 0000 [#1] PREEMPT SMP PTI
      CPU: 3 PID: 16923 Comm: gtk-update-icon Not tainted 4.19.51 #42
      Hardware name: Gigabyte Technology Co., Ltd. Z97X-Gaming G1/Z97X-Gaming G1, BIOS F9 07/31/2015
      RIP: 0010:create_empty_buffers+0x24/0x100
      Code: cd 0f 1f 44 00 00 0f 1f 44 00 00 41 54 49 89 d4 ba 01 00 00 00 55 53 48 89 fb e8 97 fe ff ff 48 89 c5 48 89 c2 eb 03 48 89 ca <48> 8b 4a 08 4c 09 22 48 85 c9 75 f1 48 89 6a 08 48 8b 43 18 48 8d
      RSP: 0018:ffff927ac1b37bf8 EFLAGS: 00010286
      RAX: 0000000000000000 RBX: fffff2d4429fd740 RCX: 0000000100097149
      RDX: 0000000000000000 RSI: 0000000000000082 RDI: ffff9075a99fbe00
      RBP: 0000000000000000 R08: fffff2d440949cc8 R09: 00000000000960c0
      R10: 0000000000000002 R11: 0000000000000000 R12: 0000000000000000
      R13: ffff907601f18360 R14: 0000000000002000 R15: 0000000000001000
      FS:  00007fb55b288bc0(0000) GS:ffff90761f8c0000(0000) knlGS:0000000000000000
      CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      CR2: 0000000000000008 CR3: 000000007aebc002 CR4: 00000000001606e0
      Call Trace:
       create_page_buffers+0x4d/0x60
       __block_write_begin_int+0x8e/0x5a0
       ? ext4_inode_attach_jinode.part.82+0xb0/0xb0
       ? jbd2__journal_start+0xd7/0x1f0
       ext4_da_write_begin+0x112/0x3d0
       generic_perform_write+0xf1/0x1b0
       ? file_update_time+0x70/0x140
       __generic_file_write_iter+0x141/0x1a0
       ext4_file_write_iter+0xef/0x3b0
       __vfs_write+0x17e/0x1e0
       vfs_write+0xa5/0x1a0
       ksys_write+0x57/0xd0
       do_syscall_64+0x55/0x160
       entry_SYSCALL_64_after_hwframe+0x44/0xa9
      
      Tetsuo then noticed that this is because the __memcg_kmem_charge_memcg
      fails __GFP_NOFAIL charge when the kmem limit is reached.  This is a wrong
      behavior because nofail allocations are not allowed to fail.  Normal
      charge path simply forces the charge even if that means to cross the
      limit.  Kmem accounting should be doing the same.
      
      Link: http://lkml.kernel.org/r/20190906125608.32129-1-mhocko@kernel.orgSigned-off-by: default avatarMichal Hocko <mhocko@suse.com>
      Reported-by: default avatarThomas Lindroth <thomas.lindroth@gmail.com>
      Debugged-by: default avatarTetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
      Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Thomas Lindroth <thomas.lindroth@gmail.com>
      Cc: Shakeel Butt <shakeelb@google.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e55d9d9b
  2. 24 Sep, 2019 39 commits