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Parav Pandit f9acb02096 RDMA/core: Sync unregistration with netlink commands 
[ Upstream commit 01b671170d ]

When the rdma device is getting removed, get resource info can race with
device removal, as below:

      CPU-0                                  CPU-1
    --------                               --------
    rdma_nl_rcv_msg()
       nldev_res_get_cq_dumpit()
          mutex_lock(device_lock);
          get device reference
          mutex_unlock(device_lock);        [..]
                                            ib_unregister_device()
                                            /* Valid reference to
                                             * device->dev exists.
                                             */
                                             ib_dealloc_device()

          [..]
          provider->fill_res_entry();

Even though device object is not freed, fill_res_entry() can get called on
device which doesn't have a driver anymore. Kernel core device reference
count is not sufficient, as this only keeps the structure valid, and
doesn't guarantee the driver is still loaded.

Similar race can occur with device renaming and device removal, where
device_rename() tries to rename a unregistered device. While this is fine
for devices of a class which are not net namespace aware, but it is
incorrect for net namespace aware class coming in subsequent series.  If a
class is net namespace aware, then the below [1] call trace is observed in
above situation.

Therefore, to avoid the race, keep a reference count and let device
unregistration wait until all netlink users drop the reference.

[1] Call trace:
kernfs: ns required in 'infiniband' for 'mlx5_0'
WARNING: CPU: 18 PID: 44270 at fs/kernfs/dir.c:842 kernfs_find_ns+0x104/0x120
libahci i2c_core mlxfw libata dca [last unloaded: devlink]
RIP: 0010:kernfs_find_ns+0x104/0x120
Call Trace:
kernfs_find_and_get_ns+0x2e/0x50
sysfs_rename_link_ns+0x40/0xb0
device_rename+0xb2/0xf0
ib_device_rename+0xb3/0x100 [ib_core]
nldev_set_doit+0x165/0x190 [ib_core]
rdma_nl_rcv_msg+0x249/0x250 [ib_core]
? netlink_deliver_tap+0x8f/0x3e0
rdma_nl_rcv+0xd6/0x120 [ib_core]
netlink_unicast+0x17c/0x230
netlink_sendmsg+0x2f0/0x3e0
sock_sendmsg+0x30/0x40
__sys_sendto+0xdc/0x160

Fixes: da5c850782 ("RDMA/nldev: add driver-specific resource tracking")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2019-02-12 20:02:10 +01:00
arch ARM: OMAP2+: hwmod: Fix some section annotations 2019-02-12 20:02:08 +01:00
block block: use rcu_work instead of call_rcu to avoid sleep in softirq 2019-01-22 21:09:57 +01:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: aes_ti - disable interrupts while accessing S-box 2019-02-12 20:02:06 +01:00
Documentation mm, proc: be more verbose about unstable VMA flags in /proc/<pid>/smaps 2019-01-26 09:20:51 +01:00
drivers RDMA/core: Sync unregistration with netlink commands 2019-02-12 20:02:10 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs dlm: Don't swamp the CPU with callbacks queued during recovery 2019-02-12 20:02:06 +01:00
include RDMA/core: Sync unregistration with netlink commands 2019-02-12 20:02:10 +01:00
init kbuild: Disable LD_DEAD_CODE_DATA_ELIMINATION with ftrace & GCC <= 4.7 2019-01-22 21:09:54 +01:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel genirq/affinity: Spread IRQs to all available NUMA nodes 2019-02-12 20:02:05 +01:00
lib fix int_sqrt64() for very large numbers 2019-01-22 21:09:55 +01:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
mm mm: migrate: don't rely on __PageMovable() of newpage after unlocking it 2019-02-06 17:27:44 +01:00
net ipv6: Consider sk_bound_dev_if when binding a socket to an address 2019-02-06 17:27:39 +01:00
samples samples: bpf: fix: error handling regarding kprobe_events 2019-01-26 09:20:42 +01:00
scripts modpost: validate symbol names also in find_elf_symbol 2019-02-12 20:02:09 +01:00
security selinux: always allow mounting submounts 2019-01-26 09:20:42 +01:00
sound ASoC: Intel: mrfld: fix uninitialized variable access 2019-02-12 20:02:04 +01:00
tools perf tools: Add Hygon Dhyana support 2019-02-12 20:02:09 +01:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: arm/arm64: vgic: Fix off-by-one bug in vgic_get_irq() 2019-01-09 17:46:04 +01:00
.clang-format page cache: Convert find_get_pages_contig to XArray 2018-10-21 10:46:34 -04:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap mailmap: Update email for Punit Agrawal 2018-11-05 10:02:11 +00:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: update entry for MMP platform 2018-12-03 12:39:57 -08:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-12-21 14:21:17 -08:00
Makefile Linux 4.20.7 2019-02-06 17:27:45 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.