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Gavin Shan 60bb8b451c vhost: Add smp_rmb() in vhost_vq_avail_empty() 
commit 22e1992cf7 upstream.

A smp_rmb() has been missed in vhost_vq_avail_empty(), spotted by
Will. Otherwise, it's not ensured the available ring entries pushed
by guest can be observed by vhost in time, leading to stale available
ring entries fetched by vhost in vhost_get_vq_desc(), as reported by
Yihuang Yu on NVidia's grace-hopper (ARM64) platform.

  /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64      \
  -accel kvm -machine virt,gic-version=host -cpu host          \
  -smp maxcpus=1,cpus=1,sockets=1,clusters=1,cores=1,threads=1 \
  -m 4096M,slots=16,maxmem=64G                                 \
  -object memory-backend-ram,id=mem0,size=4096M                \
   :                                                           \
  -netdev tap,id=vnet0,vhost=true                              \
  -device virtio-net-pci,bus=pcie.8,netdev=vnet0,mac=52:54:00:f1:26:b0
   :
  guest# netperf -H 10.26.1.81 -l 60 -C -c -t UDP_STREAM
  virtio_net virtio0: output.0:id 100 is not a head!

Add the missed smp_rmb() in vhost_vq_avail_empty(). When tx_can_batch()
returns true, it means there's still pending tx buffers. Since it might
read indices, so it still can bypass the smp_rmb() in vhost_get_vq_desc().
Note that it should be safe until vq->avail_idx is changed by commit
275bf960ac ("vhost: better detection of available buffers").

Fixes: 275bf960ac ("vhost: better detection of available buffers")
Cc: <stable@kernel.org> # v4.11+
Reported-by: Yihuang Yu <yihyu@redhat.com>
Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20240328002149.1141302-2-gshan@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-05-02 16:17:08 +02:00
arch x86/mm/pat: fix VM_PAT handling in COW mappings 2024-04-13 12:50:17 +02:00
block block: prevent division by zero in blk_rq_stat_sum() 2024-04-13 12:50:16 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-25 11:49:16 +02:00
crypto crypto: af_alg - Work around empty control messages without MSG_MORE 2024-03-26 18:22:43 -04:00
Documentation x86/cpu: Enable STIBP on AMD if Automatic IBRS is enabled 2024-04-13 12:50:11 +02:00
drivers vhost: Add smp_rmb() in vhost_vq_avail_empty() 2024-05-02 16:17:08 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs isofs: handle CDs with bad root inode but good Joliet root directory 2024-04-13 12:50:15 +02:00
include ipv6: fix race condition between ipv6_get_ifaddr and ipv6_del_addr 2024-05-02 16:17:08 +02:00
init initramfs: fix populate_initrd_image() section mismatch 2024-04-13 12:50:17 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:18:35 +01:00
kernel tracing: hide unused ftrace_event_id_fops 2024-05-02 16:17:08 +02:00
lib kobject: Fix slab-out-of-bounds in fill_kobj_path() 2023-11-08 11:22:17 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm x86/mm/pat: fix VM_PAT handling in COW mappings 2024-04-13 12:50:17 +02:00
net ipv6: fix race condition between ipv6_get_ifaddr and ipv6_del_addr 2024-05-02 16:17:08 +02:00
samples samples/bpf: Fix buffer overflow in tcp_basertt 2023-08-11 11:45:03 +02:00
scripts kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1 2024-04-13 12:50:06 +02:00
security smack: Handle SMACK64TRANSMUTE in smack_inode_setsecurity() 2024-04-13 12:50:03 +02:00
sound ALSA: hda/realtek: Update Panasonic CF-SZ6 quirk to support headset with microphone 2024-04-13 12:50:14 +02:00
tools tools: iio: replace seekdir() in iio_generic_buffer 2024-04-13 12:50:16 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-13 12:50:03 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.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 libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
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 MAINTAINERS: r8169: Update path to the driver 2023-11-08 11:22:19 +01:00
Makefile Linux 4.19.312 2024-04-13 12:50:17 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.