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David Hildenbrand fcd06731f5 KVM: s390: vsie: fix some corner-cases when grabbing vsie pages 
commit 5f230f41fd upstream.

We try to reuse the same vsie page when re-executing the vsie with a
given SCB address. The result is that we use the same shadow SCB --
residing in the vsie page -- and can avoid flushing the TLB when
re-running the vsie on a CPU.

So, when we allocate a fresh vsie page, or when we reuse a vsie page for
a different SCB address -- reusing the shadow SCB in different context --
we set ihcpu=0xffff to trigger the flush.

However, after we looked up the SCB address in the radix tree, but before
we grabbed the vsie page by raising the refcount to 2, someone could reuse
the vsie page for a different SCB address, adjusting page->index and the
radix tree. In that case, we would be reusing the vsie page with a
wrong page->index.

Another corner case is that we might set the SCB address for a vsie
page, but fail the insertion into the radix tree. Whoever would reuse
that page would remove the corresponding radix tree entry -- which might
now be a valid entry pointing at another page, resulting in the wrong
vsie page getting removed from the radix tree.

Let's handle such races better, by validating that the SCB address of a
vsie page didn't change after we grabbed it (not reuse for a different
SCB; the alternative would be performing another tree lookup), and by
setting the SCB address to invalid until the insertion in the tree
succeeded (SCB addresses are aligned to 512, so ULONG_MAX is invalid).

These scenarios are rare, the effects a bit unclear, and these issues were
only found by code inspection. Let's CC stable to be safe.

Fixes: a3508fbe9d ("KVM: s390: vsie: initial support for nested virtualization")
Cc: stable@vger.kernel.org
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Tested-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Message-ID: <20250107154344.1003072-2-david@redhat.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-02-17 09:40:16 +01:00
arch
block partitions: ldm: remove the initial kernel-doc notation 2025-02-08 09:51:43 +01:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: ecc - Prevent ecc_digits_from_bytes from reading too many bytes 2025-01-09 13:31:52 +01:00
Documentation dt-bindings: mfd: bd71815: Fix rsense and typos 2025-02-08 09:51:52 +01:00
drivers drm/rockchip: cdn-dp: Use drm_connector_helper_hpd_irq_event() 2025-02-17 09:40:16 +01:00
fs binfmt_flat: Fix integer overflow bug on 32 bit systems 2025-02-17 09:40:16 +01:00
include KVM: Explicitly verify target vCPU is online in kvm_get_vcpu() 2025-02-17 09:40:16 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-09 10:32:46 +01:00
io_uring io_uring/uring_cmd: use cached cmd_op in io_uring_cmd_sock() 2025-02-08 09:52:33 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-09 10:32:54 +01:00
kernel printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX 2025-02-17 09:40:04 +01:00
lib lockdep: Fix upper limit for LOCKDEP_*_BITS configs 2025-02-17 09:40:03 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm cachestat: fix page cache statistics permission checking 2025-02-01 18:37:54 +01:00
net rxrpc: Fix call state set to not include the SERVER_SECURING state 2025-02-17 09:40:14 +01:00
rust rust: macros: fix documentation of the paste! macro 2024-12-09 10:32:25 +01:00
samples samples/landlock: Fix possible NULL dereference in parse_path() 2025-02-08 09:51:57 +01:00
scripts kbuild: switch from lz4c to lz4 for compression 2025-02-08 09:52:35 +01:00
security tomoyo: don't emit warning in tomoyo_write_control() 2025-02-17 09:40:07 +01:00
sound ALSA: hda/realtek: Enable Mute LED on HP Laptop 14s-fq1xxx 2025-02-17 09:40:15 +01:00
tools udp: gso: do not drop small packets when PMTU reduces 2025-02-17 09:40:12 +01:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.77 2025-02-11 09:37:33 +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.