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Jason Gunthorpe a862192e92 RDMA/mlx5: Prevent prefetch from racing with implicit destruction 
Prefetch work in mlx5_ib_prefetch_mr_work can be queued and able to run
concurrently with destruction of the implicit MR. The num_deferred_work
was intended to serialize this, but there is a race:

       CPU0                                          CPU1

    mlx5_ib_free_implicit_mr()
      xa_erase(odp_mkeys)
      synchronize_srcu()
      __xa_erase(implicit_children)
                                      mlx5_ib_prefetch_mr_work()
                                        pagefault_mr()
                                         pagefault_implicit_mr()
                                          implicit_get_child_mr()
                                           xa_cmpxchg()
                                        atomic_dec_and_test(num_deferred_mr)
      wait_event(imr->q_deferred_work)
      ib_umem_odp_release(odp_imr)
        kfree(odp_imr)

At this point in mlx5_ib_free_implicit_mr() the implicit_children list is
supposed to be empty forever so that destroy_unused_implicit_child_mr()
and related are not and will not be running.

Since it is not empty the destroy_unused_implicit_child_mr() flow ends up
touching deallocated memory as mlx5_ib_free_implicit_mr() already tore down the
imr parent.

The solution is to flush out the prefetch wq by driving num_deferred_work
to zero after creation of new prefetch work is blocked.

Fixes: 5256edcb98 ("RDMA/mlx5: Rework implicit ODP destroy")
Link: https://lore.kernel.org/r/20200719065435.130722-1-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
History 2020-07-21 13:51:35 -03:00
arch Xtensa fixes for v5.8: 2020-07-12 13:29:07 -07:00
block block-5.8-2020-07-10 2020-07-10 09:55:46 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock() 2020-06-18 17:09:54 +10:00
Documentation Extend coding-style with inclusive-terminology recommendations. 2020-07-10 21:15:25 -07:00
drivers RDMA/mlx5: Prevent prefetch from racing with implicit destruction 2020-07-21 13:51:35 -03:00
fs io_uring-5.8-2020-07-12 2020-07-12 12:17:58 -07:00
include RISC-V Fixes for 5.8-rc5 (ideally) 2020-07-11 19:22:46 -07:00
init kbuild: fix CONFIG_CC_CAN_LINK(_STATIC) for cross-compilation with Clang 2020-07-02 00:57:45 +09:00
ipc mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
kernel RISC-V Fixes for 5.8-rc5 (ideally) 2020-07-11 19:22:46 -07:00
lib RISC-V Fixes for 5.8-rc5 (ideally) 2020-07-11 19:22:46 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Fix gfs2 readahead deadlocks 2020-07-10 08:53:21 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-07-10 18:16:22 -07:00
samples samples/vfs: avoid warning in statx override 2020-07-03 16:15:25 -07:00
scripts kbuild: Move -Wtype-limits to W=2 2020-07-09 18:00:56 -07:00
security integrity/ima: switch to using __kernel_read 2020-07-08 08:27:57 +02:00
sound sound fixes for 5.8-rc5 2020-07-08 11:07:09 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-07-10 18:16:22 -07:00
usr bpfilter: match bit size of bpfilter_umh to that of the kernel 2020-05-17 18:52:01 +09:00
virt kvm: use more precise cast and do not drop __user 2020-07-02 05:39:31 -04:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Do not track defconfig from make savedefconfig 2020-07-05 16:15:46 +09:00
.mailmap MAINTAINERS: update email address for Gerald Schaefer 2020-07-10 15:06:49 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS mailmap: change email for Ricardo Ribalda 2020-05-25 18:59:59 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-07-10 18:16:22 -07:00
Makefile Linux 5.8-rc5 2020-07-12 16:34:50 -07:00
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.