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.
code
Clone this repository
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Pull scheduler fix from Borislav Petkov:
- Make sure tasks are thawed exactly and only once to avoid their state
getting corrupted
* tag 'sched_urgent_for_v6.7_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
freezer,sched: Do not restore saved_state of a thawed task
Pull perf event fix from Borislav Petkov:
- Make sure perf event size validation is done on every event in the
group
* tag 'perf_urgent_for_v6.7_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: Fix perf_event_validate_size()
It is possible for a task to be thawed multiple times when mixing the
*legacy* cgroup freezer and system-wide freezer. To do this, freeze the
cgroup, do system-wide freeze/thaw, then thaw the cgroup. When this
happens, then a stale saved_state can be written to the task's state
and cause task to hang indefinitely. Fix this by only trying to thaw
tasks that are actually frozen.
This change also has the marginal benefit avoiding unnecessary
wake_up_state(p, TASK_FROZEN) if we know the task is already thawed.
There is not possibility of time-of-compare/time-of-use race when we skip
the wake_up_state because entering/exiting TASK_FROZEN is guarded by
freezer_lock.
Fixes: 8f0eed4a78a8 ("freezer,sched: Use saved_state to reduce some spurious wakeups")
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Abhijeet Dharmapurikar <quic_adharmap@quicinc.com>
Link: https://lore.kernel.org/r/20231120-freezer-state-multiple-thaws-v1-1-f2e1dd7ce5a2@quicinc.com
Pull x86 fixes from Borislav Petkov:
- Add a forgotten CPU vendor check in the AMD microcode post-loading
callback so that the callback runs only on AMD
- Make sure SEV-ES protocol negotiation happens only once and on the
BSP
* tag 'x86_urgent_for_v6.7_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/CPU/AMD: Check vendor in the AMD microcode callback
x86/sev: Fix kernel crash due to late update to read-only ghcb_version
Budimir noted that perf_event_validate_size() only checks the size of
the newly added event, even though the sizes of all existing events
can also change due to not all events having the same read_format.
When we attach the new event, perf_group_attach(), we do re-compute
the size for all events.
Fixes: a723968c0ed3 ("perf: Fix u16 overflows")
Reported-by: Budimir Markovic <markovicbudimir@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Pull kvm fixes from Paolo Bonzini:
"Generic:
- Set .owner for various KVM file_operations so that files refcount
the KVM module until KVM is done executing _all_ code, including
the last few instructions of kvm_put_kvm(). And then revert the
misguided attempt to rely on "struct kvm" refcounts to pin
KVM-the-module.
ARM:
- Do not redo the mapping of vLPIs, if they have already been mapped
s390:
- Do not leave bits behind in PTEs
- Properly catch page invalidations that affect the prefix of a
nested guest
x86:
- When checking if a _running_ vCPU is "in-kernel", i.e. running at
CPL0, get the CPL directly instead of relying on
preempted_in_kernel (which is valid if and only if the vCPU was
preempted, i.e. NOT running).
- Fix a benign "return void" that was recently introduced.
Selftests:
- Makefile tweak for dependency generation
- '-Wformat' fix"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: SVM: Update EFER software model on CR0 trap for SEV-ES
KVM: selftests: add -MP to CFLAGS
KVM: selftests: Actually print out magic token in NX hugepages skip message
KVM: x86: Remove 'return void' expression for 'void function'
Revert "KVM: Prevent module exit until all VMs are freed"
KVM: Set file_operations.owner appropriately for all such structures
KVM: x86: Get CPL directly when checking if loaded vCPU is in kernel mode
KVM: arm64: GICv4: Do not perform a map to a mapped vLPI
KVM: s390/mm: Properly reset no-dat
KVM: s390: vsie: fix wrong VIR 37 when MSO is used
Commit in Fixes added an AMD-specific microcode callback. However, it
didn't check the CPU vendor the kernel runs on explicitly.
The only reason the Zenbleed check in it didn't run on other x86 vendors
hardware was pure coincidental luck:
if (!cpu_has_amd_erratum(c, amd_zenbleed))
return;
gives true on other vendors because they don't have those families and
models.
However, with the removal of the cpu_has_amd_erratum() in
05f5f73936fa ("x86/CPU/AMD: Drop now unused CPU erratum checking function")
that coincidental condition is gone, leading to the zenbleed check
getting executed on other vendors too.
Add the explicit vendor check for the whole callback as it should've
been done in the first place.
Fixes: 522b1d69219d ("x86/cpu/amd: Add a Zenbleed fix")
Cc: <stable@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231201184226.16749-1-bp@alien8.de
Pull tracing fixes from Steven Rostedt::
"Eventfs fixes:
- With the usage of simple_recursive_remove() recommended by Al Viro,
the code should not be calling "d_invalidate()" itself. Doing so is
causing crashes. The code was calling d_invalidate() on the race of
trying to look up a file while the parent was being deleted. This
was detected, and the added dentry was having d_invalidate() called
on it, but the deletion of the directory was also calling
d_invalidate() on that same dentry.
- A fix to not free the eventfs_inode (ei) until the last dput() was
called on its ei->dentry made the ei->dentry exist even after it
was marked for free by setting the ei->is_freed. But code elsewhere
still was checking if ei->dentry was NULL if ei->is_freed is set
and would trigger WARN_ON if that was the case. That's no longer
true and there should not be any warnings when it is true.
- Use GFP_NOFS for allocations done under eventfs_mutex. The
eventfs_mutex can be taken on file system reclaim, make sure that
allocations done under that mutex do not trigger file system
reclaim.
- Clean up code by moving the taking of inode_lock out of the helper
functions and into where they are needed, and not use the parameter
to know to take it or not. It must always be held but some callers
of the helper function have it taken when they were called.
- Warn if the inode_lock is not held in the helper functions.
- Warn if eventfs_start_creating() is called without a parent. As
eventfs is underneath tracefs, all files created will have a parent
(the top one will have a tracefs parent).
Tracing update:
- Add Mathieu Desnoyers as an official reviewer of the tracing subsystem"
* tag 'trace-v6.7-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
MAINTAINERS: TRACING: Add Mathieu Desnoyers as Reviewer
eventfs: Make sure that parent->d_inode is locked in creating files/dirs
eventfs: Do not allow NULL parent to eventfs_start_creating()
eventfs: Move taking of inode_lock into dcache_dir_open_wrapper()
eventfs: Use GFP_NOFS for allocation when eventfs_mutex is held
eventfs: Do not invalidate dentry in create_file/dir_dentry()
eventfs: Remove expectation that ei->is_freed means ei->dentry == NULL
Pull powerpc fix from Michael Ellerman:
- Fix stack teardown in ftrace_no_trace, seen as crashes doing CPU
hotplug while ftrace is active.
Thanks to Naveen N Rao.
* tag 'powerpc-6.7-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/ftrace: Fix stack teardown in ftrace_no_trace
In general, activating long mode involves setting the EFER_LME bit in
the EFER register and then enabling the X86_CR0_PG bit in the CR0
register. At this point, the EFER_LMA bit will be set automatically by
hardware.
In the case of SVM/SEV guests where writes to CR0 are intercepted, it's
necessary for the host to set EFER_LMA on behalf of the guest since
hardware does not see the actual CR0 write.
In the case of SEV-ES guests where writes to CR0 are trapped instead of
intercepted, the hardware *does* see/record the write to CR0 before
exiting and passing the value on to the host, so as part of enabling
SEV-ES support commit f1c6366e3043 ("KVM: SVM: Add required changes to
support intercepts under SEV-ES") dropped special handling of the
EFER_LMA bit with the understanding that it would be set automatically.
However, since the guest never explicitly sets the EFER_LMA bit, the
host never becomes aware that it has been set. This becomes problematic
when userspace tries to get/set the EFER values via
KVM_GET_SREGS/KVM_SET_SREGS, since the EFER contents tracked by the host
will be missing the EFER_LMA bit, and when userspace attempts to pass
the EFER value back via KVM_SET_SREGS it will fail a sanity check that
asserts that EFER_LMA should always be set when X86_CR0_PG and EFER_LME
are set.
Fix this by always inferring the value of EFER_LMA based on X86_CR0_PG
and EFER_LME, regardless of whether or not SEV-ES is enabled.
Fixes: f1c6366e3043 ("KVM: SVM: Add required changes to support intercepts under SEV-ES")
Reported-by: Peter Gonda <pgonda@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210507165947.2502412-2-seanjc@google.com>
[A two year old patch that was revived after we noticed the failure in
KVM_SET_SREGS and a similar patch was posted by Michael Roth. This is
Sean's patch, but with Michael's more complete commit message. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
A write-access violation page fault kernel crash was observed while running
cpuhotplug LTP testcases on SEV-ES enabled systems. The crash was
observed during hotplug, after the CPU was offlined and the process
was migrated to different CPU. setup_ghcb() is called again which
tries to update ghcb_version in sev_es_negotiate_protocol(). Ideally this
is a read_only variable which is initialised during booting.
Trying to write it results in a pagefault:
BUG: unable to handle page fault for address: ffffffffba556e70
#PF: supervisor write access in kernel mode
#PF: error_code(0x0003) - permissions violation
[ ...]
Call Trace:
<TASK>
? __die_body.cold+0x1a/0x1f
? __die+0x2a/0x35
? page_fault_oops+0x10c/0x270
? setup_ghcb+0x71/0x100
? __x86_return_thunk+0x5/0x6
? search_exception_tables+0x60/0x70
? __x86_return_thunk+0x5/0x6
? fixup_exception+0x27/0x320
? kernelmode_fixup_or_oops+0xa2/0x120
? __bad_area_nosemaphore+0x16a/0x1b0
? kernel_exc_vmm_communication+0x60/0xb0
? bad_area_nosemaphore+0x16/0x20
? do_kern_addr_fault+0x7a/0x90
? exc_page_fault+0xbd/0x160
? asm_exc_page_fault+0x27/0x30
? setup_ghcb+0x71/0x100
? setup_ghcb+0xe/0x100
cpu_init_exception_handling+0x1b9/0x1f0
The fix is to call sev_es_negotiate_protocol() only in the BSP boot phase,
and it only needs to be done once in any case.
[ mingo: Refined the changelog. ]
Fixes: 95d33bfaa3e1 ("x86/sev: Register GHCB memory when SEV-SNP is active")
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Co-developed-by: Bo Gan <bo.gan@broadcom.com>
Signed-off-by: Bo Gan <bo.gan@broadcom.com>
Signed-off-by: Ashwin Dayanand Kamat <ashwin.kamat@broadcom.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/1701254429-18250-1-git-send-email-kashwindayan@vmware.com
Pull parisc architecture fixes from Helge Deller:
"This patchset fixes and enforces correct section alignments for the
ex_table, altinstructions, parisc_unwind, jump_table and bug_table
which are created by inline assembly.
Due to not being correctly aligned at link & load time they can
trigger unnecessarily the kernel unaligned exception handler at
runtime. While at it, I switched the bug table to use relative
addresses which reduces the size of the table by half on 64-bit.
We still had the ENOSYM and EREMOTERELEASE errno symbols as left-overs
from HP-UX, which now trigger build-issues with glibc. We can simply
remove them.
Most of the patches are tagged for stable kernel series.
Summary:
- Drop HP-UX ENOSYM and EREMOTERELEASE return codes to avoid glibc
build issues
- Fix section alignments for ex_table, altinstructions, parisc unwind
table, jump_table and bug_table
- Reduce size of bug_table on 64-bit kernel by using relative
pointers"
* tag 'parisc-for-6.7-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
parisc: Reduce size of the bug_table on 64-bit kernel by half
parisc: Drop the HP-UX ENOSYM and EREMOTERELEASE error codes
parisc: Use natural CPU alignment for bug_table
parisc: Ensure 32-bit alignment on parisc unwind section
parisc: Mark lock_aligned variables 16-byte aligned on SMP
parisc: Mark jump_table naturally aligned
parisc: Mark altinstructions read-only and 32-bit aligned
parisc: Mark ex_table entries 32-bit aligned in uaccess.h
parisc: Mark ex_table entries 32-bit aligned in assembly.h
In order to make sure I get CC'd on tracing changes for which my input
would be relevant, add my name as reviewer of the TRACING subsystem.
Link: https://lore.kernel.org/linux-trace-kernel/20231115155018.8236-1-mathieu.desnoyers@efficios.com
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Pull gpio fix from Bartosz Golaszewski:
- fix an error path after a failed export in sysfs code
* tag 'gpio-fixes-for-v6.7-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux:
gpiolib: sysfs: Fix error handling on failed export