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Demi Marie Obenour 062eae34a5 xen/gntdev: Avoid blocking in unmap_grant_pages()
commit dbe97cff7d upstream.

unmap_grant_pages() currently waits for the pages to no longer be used.
In https://github.com/QubesOS/qubes-issues/issues/7481, this lead to a
deadlock against i915: i915 was waiting for gntdev's MMU notifier to
finish, while gntdev was waiting for i915 to free its pages.  I also
believe this is responsible for various deadlocks I have experienced in
the past.

Avoid these problems by making unmap_grant_pages async.  This requires
making it return void, as any errors will not be available when the
function returns.  Fortunately, the only use of the return value is a
WARN_ON(), which can be replaced by a WARN_ON when the error is
detected.  Additionally, a failed call will not prevent further calls
from being made, but this is harmless.

Because unmap_grant_pages is now async, the grant handle will be sent to
INVALID_GRANT_HANDLE too late to prevent multiple unmaps of the same
handle.  Instead, a separate bool array is allocated for this purpose.
This wastes memory, but stuffing this information in padding bytes is
too fragile.  Furthermore, it is necessary to grab a reference to the
map before making the asynchronous call, and release the reference when
the call returns.

It is also necessary to guard against reentrancy in gntdev_map_put(),
and to handle the case where userspace tries to map a mapping whose
contents have not all been freed yet.

Fixes: 745282256c ("xen/gntdev: safely unmap grants in case they are still in use")
Cc: stable@vger.kernel.org
Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220622022726.2538-1-demi@invisiblethingslab.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-04-19 17:50:39 +08:00
arch arm64: mm: Don't invalidate FROM_DEVICE buffers at start of DMA transfer 2023-04-19 17:50:37 +08:00
block block: Fix handling of offline queues in blk_mq_alloc_request_hctx() 2023-04-19 17:50:34 +08:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2023-04-19 17:50:34 +08:00
crypto crypto: memneq - move into lib/ 2023-04-19 17:50:35 +08:00
Documentation x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data 2023-04-19 17:50:28 +08:00
drivers xen/gntdev: Avoid blocking in unmap_grant_pages() 2023-04-19 17:50:39 +08:00
fs btrfs: add error messages to all unrecognized mount options 2023-04-19 17:50:39 +08:00
include random: quiet urandom warning ratelimit suppression message 2023-04-19 17:50:38 +08:00
init Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug 2023-04-19 17:50:04 +08:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2023-04-19 17:49:52 +08:00
kernel bpf: Fix calling global functions from BPF_PROG_TYPE_EXT programs 2023-04-19 17:50:37 +08:00
lib crypto: memneq - move into lib/ 2023-04-19 17:50:35 +08:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm init: Initialize noop_backing_dev_info early 2023-04-19 17:50:34 +08:00
net net: openvswitch: fix parsing of nw_proto for IPv6 fragments 2023-04-19 17:50:38 +08:00
samples samples/landlock: Format with clang-format 2023-04-19 17:50:01 +08:00
scripts faddr2line: Fix overlapping text section failures, the sequel 2023-04-19 17:50:34 +08:00
security KEYS: trusted: tpm2: Fix migratable logic 2023-04-19 17:50:26 +08:00
sound ALSA: hda/realtek: Add quirk for Clevo NS50PU 2023-04-19 17:50:38 +08:00
tools selftests/bpf: Add selftest for calling global functions from freplace 2023-04-19 17:50:37 +08:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2023-04-19 17:44:58 +08:00
virt KVM: avoid NULL pointer dereference in kvm_dirty_ring_push 2023-04-19 17:47:52 +08:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +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: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
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 MAINTAINERS: add git tree for random.c 2023-04-19 17:49:03 +08:00
Makefile Linux 5.15.50 2023-04-19 17:50:37 +08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.