What is the meaning of 'Redzone' error?

Issue

• Customer got following messages and want to know the meaning of the error message.

  Apr 18 09:11:48 SKDWDINDEX kernel: Slab corruption: start=ffff8101a97f3448, len=168
  Apr 18 09:11:48 SKDWDINDEX kernel: Redzone: 0x5a2cf071/0x5a2cf071.
  Apr 18 09:11:48 SKDWDINDEX kernel: Last user: [<ffffffff8032f930>](cfq_free_io_context+0x30/0x6d)
  Apr 18 09:11:48 SKDWDINDEX kernel: 090: 80 dc d2 25 02 81 ff ff 6b 6b 6b 6b 6b 6b 6b 6b
  Apr 18 09:11:48 SKDWDINDEX kernel: Prev obj: start=ffff8101a97f3388, len=168
  Apr 18 09:11:48 SKDWDINDEX kernel: Redzone: 0x5a2cf071/0x5a2cf071.
  Apr 18 09:11:48 SKDWDINDEX kernel: Last user: [<ffffffff8032f930>](cfq_free_io_context+0x30/0x6d)
  Apr 18 09:11:48 SKDWDINDEX kernel: 000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
  Apr 18 09:11:48 SKDWDINDEX kernel: 010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
  Apr 18 09:11:48 SKDWDINDEX kernel: Next obj: start=ffff8101a97f3508, len=168
  Apr 18 09:11:48 SKDWDINDEX kernel: Redzone: 0x170fc2a5/0x170fc2a5.
  Apr 18 09:11:48 SKDWDINDEX kernel: Last user: [<ffffffff8021d34a>](cfq_set_request+0x3af/0x412)
  Apr 18 09:11:48 SKDWDINDEX kernel: 000: 00 00 00 00 00 00 00 00 01 00 00 00 5a 5a 5a 5a
  Apr 18 09:11:48 SKDWDINDEX kernel: 010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  Apr 19 04:02:07 SKDWDINDEX kernel: Slab corruption: start=ffff8102251aa908, len=168
  Apr 19 04:02:07 SKDWDINDEX kernel: Redzone: 0x5a2cf071/0x5a2cf071.
  Apr 19 04:02:07 SKDWDINDEX kernel: Last user: [<ffffffff8032f930>](cfq_free_io_context+0x30/0x6d)
  Apr 19 04:02:07 SKDWDINDEX kernel: 090: 50 3f 66 a1 01 81 ff ff 6b 6b 6b 6b 6b 6b 6b 6b
  Apr 19 04:02:07 SKDWDINDEX kernel: Prev obj: start=ffff8102251aa848, len=168
  Apr 19 04:02:07 SKDWDINDEX kernel: Redzone: 0x170fc2a5/0x170fc2a5.
  Apr 19 04:02:07 SKDWDINDEX kernel: Last user: [<ffffffff8021d34a>](cfq_set_request+0x3af/0x412)
  Apr 19 04:02:07 SKDWDINDEX kernel: 000: 00 00 00 00 00 00 00 00 01 00 00 00 5a 5a 5a 5a
  Apr 19 04:02:07 SKDWDINDEX kernel: 010: 08 38 7f a9 01 81 ff ff 00 00 00 00 00 00 00 00
  Apr 19 04:02:07 SKDWDINDEX kernel: Next obj: start=ffff8102251aa9c8, len=168
  Apr 19 04:02:07 SKDWDINDEX kernel: Redzone: 0x170fc2a5/0x170fc2a5.
  Apr 19 04:02:07 SKDWDINDEX kernel: Last user: [<ffffffff8021d34a>](cfq_set_request+0x3af/0x412)
  Apr 19 04:02:07 SKDWDINDEX kernel: 000: 00 00 00 00 00 00 00 00 01 00 00 00 5a 5a 5a 5a
  Apr 19 04:02:08 SKDWDINDEX kernel: 010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  Apr 19 04:02:49 SKDWDINDEX kernel: Slab corruption: start=ffff8102251aa908, len=168
  Apr 19 04:02:49 SKDWDINDEX kernel: Redzone: 0x5a2cf071/0x5a2cf071.
  Apr 19 04:02:49 SKDWDINDEX kernel: Last user: [<ffffffff8032f930>](cfq_free_io_context+0x30/0x6d)
  Apr 19 04:02:49 SKDWDINDEX kernel: 090: 10 37 66 a1 01 81 ff ff 6b 6b 6b 6b 6b 6b 6b 6b
  Apr 19 04:02:49 SKDWDINDEX kernel: Prev obj: start=ffff8102251aa848, len=168
  Apr 19 04:02:49 SKDWDINDEX kernel: Redzone: 0x170fc2a5/0x170fc2a5.
  Apr 19 04:02:49 SKDWDINDEX kernel: Last user: [<ffffffff8021d34a>](cfq_set_request+0x3af/0x412)
  Apr 19 04:02:49 SKDWDINDEX kernel: 000: 00 00 00 00 00 00 00 00 01 00 00 00 5a 5a 5a 5a
  Apr 19 04:02:49 SKDWDINDEX kernel: 010: 08 38 7f a9 01 81 ff ff 00 00 00 00 00 00 00 00
  Apr 19 04:02:49 SKDWDINDEX kernel: Next obj: start=ffff8102251aa9c8, len=168
  Apr 19 04:02:49 SKDWDINDEX kernel: Redzone: 0x170fc2a5/0x170fc2a5.
  Apr 19 04:02:49 SKDWDINDEX kernel: Last user: [<ffffffff8021d34a>](cfq_set_request+0x3af/0x412)
  Apr 19 04:02:49 SKDWDINDEX kernel: 000: 00 00 00 00 00 00 00 00 01 00 00 00 5a 5a 5a 5a
  Apr 19 04:02:49 SKDWDINDEX kernel: 010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  Apr 19 08:00:31 SKDWDINDEX kernel: Slab corruption: start=ffff8102251aa908, len=168
  Apr 19 08:00:31 SKDWDINDEX kernel: Redzone: 0x5a2cf071/0x5a2cf071.
  Apr 19 08:00:31 SKDWDINDEX kernel: Last user: [<ffffffff8032f930>](cfq_free_io_context+0x30/0x6d)
  Apr 19 08:00:31 SKDWDINDEX kernel: 090: 80 dc d2 25 02 81 ff ff 6b 6b 6b 6b 6b 6b 6b 6b
  Apr 19 08:00:31 SKDWDINDEX kernel: Prev obj: start=ffff8102251aa848, len=168
  Apr 19 08:00:31 SKDWDINDEX kernel: Redzone: 0x170fc2a5/0x170fc2a5.
  Apr 19 08:00:31 SKDWDINDEX kernel: Last user: [<ffffffff8021d34a>](cfq_set_request+0x3af/0x412)
  Apr 19 08:00:31 SKDWDINDEX kernel: 000: 00 00 00 00 00 00 00 00 01 00 00 00 5a 5a 5a 5a
  Apr 19 08:00:31 SKDWDINDEX kernel: 010: 08 38 7f a9 01 81 ff ff 00 00 00 00 00 00 00 00
  Apr 19 08:00:31 SKDWDINDEX kernel: Next obj: start=ffff8102251aa9c8, len=168
  Apr 19 08:00:31 SKDWDINDEX kernel: Redzone: 0x170fc2a5/0x170fc2a5.
  Apr 19 08:00:31 SKDWDINDEX kernel: Last user: [<ffffffff8021d34a>](cfq_set_request+0x3af/0x412)
  Apr 19 08:00:31 SKDWDINDEX kernel: 000: 00 00 00 00 00 00 00 00 01 00 00 00 5a 5a 5a 5a
  Apr 19 08:00:32 SKDWDINDEX kernel: 010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ...