power9 slab-out-of-bounds in _find_First_zero_bit

[Liam Howlett]

Hello,

When trying v5.19-rc3 on my ppc64 VM with KASANs enabled, I get the
following on boot:

[    0.174621] ==================================================================
[    0.175501] BUG: KASAN: slab-out-of-bounds in _find_first_zero_bit+0x40/0x140
[    0.176132] Read of size 8 at addr c00000000f7f0410 by task swapper/0/1
[    0.176900] 
[    0.177844] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W         5.19.0-rc3+ #8
[    0.179461] Call Trace:
[    0.179907] [c0000000119677d0] [c0000000075af350] dump_stack_lvl+0x74/0xa8 (unreliable)
[    0.181107] [c000000011967810] [c000000000632220] print_report+0x330/0x740
[    0.181977] [c0000000119678e0] [c000000000632980] kasan_report+0x100/0x1f0
[    0.182788] [c0000000119679c0] [c000000000634de4] __asan_load8+0xa4/0xe0
[    0.183560] [c0000000119679e0] [c0000000018b92b0] _find_first_zero_bit+0x40/0x140
[    0.184119] [c000000011967a20] [c0000000000c5f7c] xive_spapr_get_ipi+0xcc/0x220
[    0.184689] [c000000011967ad0] [c0000000000c1adc] xive_setup_cpu_ipi+0x1ec/0x420
[    0.185231] [c000000011967b90] [c00000000a033b3c] pSeries_smp_probe+0x44/0xd4
[    0.185825] [c000000011967bc0] [c00000000a01c77c] smp_prepare_cpus+0x62c/0x688
[    0.186359] [c000000011967cb0] [c00000000a00ea94] kernel_init_freeable+0x24c/0x520
[    0.186893] [c000000011967d90] [c000000000012b00] kernel_init+0x30/0x1c0
[    0.187395] [c000000011967e10] [c00000000000ce54] ret_from_kernel_thread+0x5c/0x64
[    0.188124] 
[    0.188429] Allocated by task 0:
[    0.188820]  kasan_save_stack+0x34/0x70
[    0.189298]  __kasan_kmalloc+0xb8/0xf0
[    0.189617]  __kmalloc+0x148/0x570
[    0.189909]  xive_spapr_init+0x478/0x6fc
[    0.190212]  pseries_init_irq+0x48/0x284
[    0.190523]  init_IRQ+0x4c/0x8c
[    0.190810]  start_kernel+0x25c/0x4d0
[    0.191130]  start_here_common+0x1c/0x20
[    0.191549] 
[    0.191845] The buggy address belongs to the object at c00000000f7f0410
[    0.191845]  which belongs to the cache kmalloc-8 of size 8
[    0.192594] The buggy address is located 0 bytes inside of
[    0.192594]  8-byte region [c00000000f7f0410, c00000000f7f0418)
[    0.193250] 
[    0.193499] The buggy address belongs to the physical page:
[    0.194324] page:c00c00000003dfc0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xf7f
[    0.195277] flags: 0x7ffff000000200(slab|node=0|zone=0|lastcpupid=0x7ffff)
[    0.196521] raw: 007ffff000000200 0000000000000000 5deadbeef0000122 c00000000f7e0300
[    0.197023] raw: 0000000000000000 0000000086660666 00000001ffffffff 0000000000000000
[    0.197558] page dumped because: kasan: bad access detected
[    0.197938] 
[    0.198128] Memory state around the buggy address:
[    0.198676]  c00000000f7f0300: fc fc fc fc 03 fc fc fc fc 03 fc fc fc fc 03 fc
[    0.199218]  c00000000f7f0380: fc fc fc 03 fc fc fc fc 03 fc fc fc fc 03 fc fc
[    0.199671] >c00000000f7f0400: fc fc 02 fc fc fc fc 04 fc fc fc fc 04 fc fc fc
[    0.200122]                          ^
[    0.200464]  c00000000f7f0480: fc 00 fc fc fc fc fa fc fc fc fc 02 fc fc fc fc
[    0.200905]  c00000000f7f0500: fa fc fc fc fc fa fc fc fc fc fa fc fc fc fc 00
[    0.201379] ==================================================================


Thanks,
Liam