Matthew Wilcox (Oracle) 3e3c658055 XArray: Fix xas_create_range() when multi-order entry present
If there is already an entry present that is of order >= XA_CHUNK_SHIFT
when we call xas_create_range(), xas_create_range() will misinterpret
that entry as a node and dereference xa_node->parent, generally leading
to a crash that looks something like this:

general protection fault, probably for non-canonical address 0xdffffc0000000001:
0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 32 Comm: khugepaged Not tainted 5.17.0-rc8-syzkaller-00003-g56e337f2cf13 #0
RIP: 0010:xa_parent_locked include/linux/xarray.h:1207 [inline]
RIP: 0010:xas_create_range+0x2d9/0x6e0 lib/xarray.c:725

It's deterministically reproducable once you know what the problem is,
but producing it in a live kernel requires khugepaged to hit a race.
While the problem has been present since xas_create_range() was
introduced, I'm not aware of a way to hit it before the page cache was
converted to use multi-index entries.

Fixes: 6b24ca4a1a8d ("mm: Use multi-index entries in the page cache")
Reported-by: syzbot+0d2b0bf32ca5cfd09f2e@syzkaller.appspotmail.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
2022-03-28 19:25:11 -04:00
..
2021-07-08 11:48:20 -07:00
2020-08-09 14:10:26 -07:00
2021-09-08 11:50:26 -07:00
2021-07-08 11:48:20 -07:00
2021-07-08 11:48:20 -07:00
2021-11-18 13:16:22 -08:00
2021-05-06 19:24:12 -07:00
2018-08-16 12:14:42 -07:00
2021-01-21 14:06:00 -07:00
2021-06-05 08:58:12 -07:00
2021-08-19 09:02:55 +09:00
2021-01-03 20:05:18 -05:00
2014-04-30 19:49:37 +01:00
2022-01-15 08:47:31 -08:00
2020-10-20 14:39:37 -07:00
2021-08-19 09:02:55 +09:00
2022-01-23 06:20:44 +02:00
2021-07-08 11:48:20 -07:00
2022-01-20 08:52:53 +02:00
2021-07-08 11:48:20 -07:00
2018-10-16 13:45:44 +02:00
2021-07-08 11:48:20 -07:00
2021-07-08 11:48:20 -07:00
2021-08-08 13:00:20 +01:00
2021-09-17 13:52:17 +01:00
2021-07-08 11:48:20 -07:00
2021-07-08 11:48:20 -07:00
2021-07-08 11:48:20 -07:00
2021-07-08 11:48:20 -07:00
2021-06-18 11:43:09 +02:00
2021-07-08 11:48:20 -07:00
2022-01-20 08:52:54 +02:00
2018-10-15 16:31:29 -04:00
2021-07-08 11:48:20 -07:00
2021-08-13 13:19:06 -06:00
2022-01-23 06:20:44 +02:00