When disassociating a device from umad we must ensure that the sysfs
access is prevented before blocking the fops, otherwise assumptions in
syfs don't hold:
CPU0 CPU1
ib_umad_kill_port() ibdev_show()
port->ib_dev = NULL
dev_name(port->ib_dev)
The prior patch made an error in moving the device_destroy(), it should
have been split into device_del() (above) and put_device() (below). At
this point we already have the split, so move the device_del() back to its
original place.
kernel stack
PF: error_code(0x0000) - not-present page
Oops: 0000 [#1] SMP DEBUG_PAGEALLOC PTI
RIP: 0010:ibdev_show+0x18/0x50 [ib_umad]
RSP: 0018:ffffc9000097fe40 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffffffffa0441120 RCX: ffff8881df514000
RDX: ffff8881df514000 RSI: ffffffffa0441120 RDI: ffff8881df1e8870
RBP: ffffffff81caf000 R08: ffff8881df1e8870 R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000003 R12: ffff88822f550b40
R13: 0000000000000001 R14: ffffc9000097ff08 R15: ffff8882238bad58
FS: 00007f1437ff3740(0000) GS:ffff888236940000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000004e8 CR3: 00000001e0dfc001 CR4: 00000000001606e0
Call Trace:
dev_attr_show+0x15/0x50
sysfs_kf_seq_show+0xb8/0x1a0
seq_read+0x12d/0x350
vfs_read+0x89/0x140
ksys_read+0x55/0xd0
do_syscall_64+0x55/0x1b0
entry_SYSCALL_64_after_hwframe+0x44/0xa9:
Fixes: cf7ad30302 ("IB/umad: Avoid destroying device while it is accessed")
Link: https://lore.kernel.org/r/20200212072635.682689-9-leon@kernel.org
Signed-off-by: Yonatan Cohen <yonatanc@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
9ea04d0df6