linux-stable.git/Documentation, branch v6.6.26

x86/bhi: Mitigate KVM by default

2024-04-10T14:36:08+00:00

commit 95a6ccbdc7199a14b71ad8901cb788ba7fb5167b upstream.

BHI mitigation mode spectre_bhi=auto does not deploy the software
mitigation by default. In a cloud environment, it is a likely scenario
where userspace is trusted but the guests are not trusted. Deploying
system wide mitigation in such cases is not desirable.

Update the auto mode to unconditionally mitigate against malicious
guests. Deploy the software sequence at VMexit in auto mode also, when
hardware mitigation is not available. Unlike the force =on mode,
software sequence is not deployed at syscalls in auto mode.

Suggested-by: Alexandre Chartre 
Signed-off-by: Pawan Gupta 
Signed-off-by: Daniel Sneddon 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Alexandre Chartre 
Reviewed-by: Josh Poimboeuf 
Signed-off-by: Daniel Sneddon 
Signed-off-by: Greg Kroah-Hartman

x86/bhi: Add BHI mitigation knob

2024-04-10T14:36:08+00:00

commit ec9404e40e8f36421a2b66ecb76dc2209fe7f3ef upstream.

Branch history clearing software sequences and hardware control
BHI_DIS_S were defined to mitigate Branch History Injection (BHI).

Add cmdline spectre_bhi={on|off|auto} to control BHI mitigation:

 auto - Deploy the hardware mitigation BHI_DIS_S, if available.
 on   - Deploy the hardware mitigation BHI_DIS_S, if available,
        otherwise deploy the software sequence at syscall entry and
	VMexit.
 off  - Turn off BHI mitigation.

The default is auto mode which does not deploy the software sequence
mitigation.  This is because of the hardening done in the syscall
dispatch path, which is the likely target of BHI.

Signed-off-by: Pawan Gupta 
Signed-off-by: Daniel Sneddon 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Alexandre Chartre 
Reviewed-by: Josh Poimboeuf 
Signed-off-by: Daniel Sneddon 
Signed-off-by: Greg Kroah-Hartman

x86/Kconfig: Remove CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT

2024-04-03T13:28:50+00:00

commit 29956748339aa8757a7e2f927a8679dd08f24bb6 upstream.

It was meant well at the time but nothing's using it so get rid of it.

Signed-off-by: Borislav Petkov (AMD) 
Acked-by: Ard Biesheuvel 
Link: https://lore.kernel.org/r/20240202163510.GDZb0Zvj8qOndvFOiZ@fat_crate.local
Signed-off-by: Greg Kroah-Hartman

docs: Restore "smart quotes" for quotes

2024-04-03T13:28:22+00:00

[ Upstream commit fe2562582bffe675721e77e00b3bf5bfa1d7aeab ]

Commit eaae75754d81 ("docs: turn off "smart quotes" in the HTML build")
disabled conversion of quote marks along with that of dashes.
Despite the short summary, the change affects not only HTML build
but also other build targets including PDF.

However, as "smart quotes" had been enabled for more than half a
decade already, quite a few readers of HTML pages are likely expecting
conversions of "foo" -> “foo” and 'bar' -> ‘bar’.

Furthermore, in LaTeX typesetting convention, it is common to use
distinct marks for opening and closing quote marks.

To satisfy such readers' expectation, restore conversion of quotes
only by setting smartquotes_action [1].

Link: [1] https://www.sphinx-doc.org/en/master/usage/configuration.html#confval-smartquotes_action
Cc: stable@vger.kernel.org  # v6.4
Signed-off-by: Akira Yokosawa 
Signed-off-by: Jonathan Corbet 
Link: https://lore.kernel.org/r/20240225094600.65628-1-akiyks@gmail.com
Signed-off-by: Sasha Levin

media: mc: Expand MUST_CONNECT flag to always require an enabled link

2024-04-03T13:28:17+00:00

[ Upstream commit b3decc5ce7d778224d266423b542326ad469cb5f ]

The MEDIA_PAD_FL_MUST_CONNECT flag indicates that the pad requires an
enabled link to stream, but only if it has any link at all. This makes
little sense, as if a pad is part of a pipeline, there are very few use
cases for an active link to be mandatory only if links exist at all. A
review of in-tree drivers confirms they all need an enabled link for
pads marked with the MEDIA_PAD_FL_MUST_CONNECT flag.

Expand the scope of the flag by rejecting pads that have no links at
all. This requires modifying the pipeline build code to add those pads
to the pipeline.

Cc: stable@vger.kernel.org # 6.1
Signed-off-by: Laurent Pinchart 
Acked-by: Sakari Ailus 
Signed-off-by: Hans Verkuil 
Signed-off-by: Sasha Levin

dt-bindings: msm: qcom, mdss: Include ommited fam-b compatible

2024-03-26T22:19:47+00:00

[ Upstream commit 3b63880de42bd3cb79c2a99949135a8f2441c088 ]

During conversion 28nm-hpm-fam-b compat got lost, add it.

Signed-off-by: Adam Skladowski 
Fixes: f7d46c5efee2 ("dt-bindings: display/msm: split qcom, mdss bindings")
Acked-by: Krzysztof Kozlowski 
Patchwork: https://patchwork.freedesktop.org/patch/575290/
Link: https://lore.kernel.org/r/20240121194221.13513-4-a39.skl@gmail.com
Signed-off-by: Dmitry Baryshkov 
Signed-off-by: Sasha Levin

ovl: add support for appending lowerdirs one by one

2024-03-26T22:19:18+00:00

[ Upstream commit 24e16e385f2272b1a9df51337a5c32d28a29c7ad ]

Add new mount options lowerdir+ and datadir+ that can be used to add
layers to lower layers stack one by one.

Unlike the legacy lowerdir mount option, special characters (i.e. colons
and cammas) are not unescaped with these new mount options.

The new mount options can be repeated to compose a large stack of lower
layers, but they may not be mixed with the lagacy lowerdir mount option,
because for displaying lower layers in mountinfo, we do not want to mix
escaped with unescaped lower layers path syntax.

Similar to data-only layer rules with the lowerdir mount option, the
datadir+ option must follow at least one lowerdir+ option and the
lowerdir+ option must not follow the datadir+ option.

If the legacy lowerdir mount option follows lowerdir+ and datadir+
mount options, it overrides them.  Sepcifically, calling:

  fsconfig(FSCONFIG_SET_STRING, "lowerdir", "", 0);

can be used to reset previously setup lower layers.

Suggested-by: Miklos Szeredi 
Link: https://lore.kernel.org/r/CAJfpegt7VC94KkRtb1dfHG8+4OzwPBLYqhtc8=QFUxpFJE+=RQ@mail.gmail.com/
Signed-off-by: Amir Goldstein 
Stable-dep-of: 2824083db76c ("ovl: Always reject mounting over case-insensitive directories")
Signed-off-by: Sasha Levin

x86/rfds: Mitigate Register File Data Sampling (RFDS)

2024-03-15T14:48:22+00:00

commit 8076fcde016c9c0e0660543e67bff86cb48a7c9c upstream.

RFDS is a CPU vulnerability that may allow userspace to infer kernel
stale data previously used in floating point registers, vector registers
and integer registers. RFDS only affects certain Intel Atom processors.

Intel released a microcode update that uses VERW instruction to clear
the affected CPU buffers. Unlike MDS, none of the affected cores support
SMT.

Add RFDS bug infrastructure and enable the VERW based mitigation by
default, that clears the affected buffers just before exiting to
userspace. Also add sysfs reporting and cmdline parameter
"reg_file_data_sampling" to control the mitigation.

For details see:
Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst

Signed-off-by: Pawan Gupta 
Signed-off-by: Dave Hansen 
Reviewed-by: Thomas Gleixner 
Acked-by: Josh Poimboeuf 
Signed-off-by: Greg Kroah-Hartman

Documentation/hw-vuln: Add documentation for RFDS

2024-03-15T14:48:22+00:00

commit 4e42765d1be01111df0c0275bbaf1db1acef346e upstream.

Add the documentation for transient execution vulnerability Register
File Data Sampling (RFDS) that affects Intel Atom CPUs.

Signed-off-by: Pawan Gupta 
Signed-off-by: Dave Hansen 
Reviewed-by: Thomas Gleixner 
Acked-by: Josh Poimboeuf 
Signed-off-by: Greg Kroah-Hartman

x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key

2024-03-06T14:48:44+00:00

commit 6613d82e617dd7eb8b0c40b2fe3acea655b1d611 upstream.

The VERW mitigation at exit-to-user is enabled via a static branch
mds_user_clear. This static branch is never toggled after boot, and can
be safely replaced with an ALTERNATIVE() which is convenient to use in
asm.

Switch to ALTERNATIVE() to use the VERW mitigation late in exit-to-user
path. Also remove the now redundant VERW in exc_nmi() and
arch_exit_to_user_mode().

Signed-off-by: Pawan Gupta 
Signed-off-by: Dave Hansen 
Link: https://lore.kernel.org/all/20240213-delay-verw-v8-4-a6216d83edb7%40linux.intel.com
Signed-off-by: Greg Kroah-Hartman