tjh.dev
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 reStructuredText 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.
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
code
Clone this repository
https://tangled.org/tjh.dev/kernel
git@gordian.tjh.dev:tjh.dev/kernel
For self-hosted knots, clone URLs may differ based on your setup.
epoll can call out to vfs_poll() with a file pointer that may race with
the last 'fput()'. That would make f_count go down to zero, and while
the ep->mtx locking means that the resulting file pointer tear-down will
be blocked until the poll returns, it means that f_count is already
dead, and any use of it won't actually get a reference to the file any
more: it's dead regardless.
Make sure we have a valid ref on the file pointer before we call down to
vfs_poll() from the epoll routines.
Link: https://lore.kernel.org/lkml/0000000000002d631f0615918f1e@google.com/
Reported-by: syzbot+045b454ab35fd82a35fb@syzkaller.appspotmail.com
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull EDAC fixes from Borislav Petkov:
- Fix error logging and check user-supplied data when injecting an
error in the versal EDAC driver
* tag 'edac_urgent_for_v6.9_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/ras/ras:
EDAC/versal: Do not log total error counts
EDAC/versal: Check user-supplied data before injecting an error
EDAC/versal: Do not register for NOC errors
Pull powerpc fixes from Michael Ellerman:
- Fix incorrect delay handling in the plpks (keystore) code
- Fix a panic when an LPAR boots with a frozen PE
Thanks to Andrew Donnellan, Gaurav Batra, Nageswara R Sastry, and Nayna
Jain.
* tag 'powerpc-6.9-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/pseries/iommu: LPAR panics during boot up with a frozen PE
powerpc/pseries: make max polling consistent for longer H_CALLs
When logging errors, the driver currently logs the total error count.
However, it should log the current error only. Fix it.
[ bp: Rewrite text. ]
Fixes: 6f15b178cd63 ("EDAC/versal: Add a Xilinx Versal memory controller driver")
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240425121942.26378-4-shubhrajyoti.datta@amd.com
Pull misc x86 fixes from Ingo Molnar:
- Remove the broken vsyscall emulation code from
the page fault code
- Fix kexec crash triggered by certain SEV RMP
table layouts
- Fix unchecked MSR access error when disabling
the x2APIC via iommu=off
* tag 'x86-urgent-2024-05-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mm: Remove broken vsyscall emulation code from the page fault code
x86/apic: Don't access the APIC when disabling x2APIC
x86/sev: Add callback to apply RMP table fixups for kexec
x86/e820: Add a new e820 table update helper
At the time of LPAR boot up, partition firmware provides Open Firmware
property ibm,dma-window for the PE. This property is provided on the PCI
bus the PE is attached to.
There are execptions where the partition firmware might not provide this
property for the PE at the time of LPAR boot up. One of the scenario is
where the firmware has frozen the PE due to some error condition. This
PE is frozen for 24 hours or unless the whole system is reinitialized.
Within this time frame, if the LPAR is booted, the frozen PE will be
presented to the LPAR but ibm,dma-window property could be missing.
Today, under these circumstances, the LPAR oopses with NULL pointer
dereference, when configuring the PCI bus the PE is attached to.
BUG: Kernel NULL pointer dereference on read at 0x000000c8
Faulting instruction address: 0xc0000000001024c0
Oops: Kernel access of bad area, sig: 7 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
Modules linked in:
Supported: Yes
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.4.0-150600.9-default #1
Hardware name: IBM,9043-MRX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NM1060_023) hv:phyp pSeries
NIP: c0000000001024c0 LR: c0000000001024b0 CTR: c000000000102450
REGS: c0000000037db5c0 TRAP: 0300 Not tainted (6.4.0-150600.9-default)
MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 28000822 XER: 00000000
CFAR: c00000000010254c DAR: 00000000000000c8 DSISR: 00080000 IRQMASK: 0
...
NIP [c0000000001024c0] pci_dma_bus_setup_pSeriesLP+0x70/0x2a0
LR [c0000000001024b0] pci_dma_bus_setup_pSeriesLP+0x60/0x2a0
Call Trace:
pci_dma_bus_setup_pSeriesLP+0x60/0x2a0 (unreliable)
pcibios_setup_bus_self+0x1c0/0x370
__of_scan_bus+0x2f8/0x330
pcibios_scan_phb+0x280/0x3d0
pcibios_init+0x88/0x12c
do_one_initcall+0x60/0x320
kernel_init_freeable+0x344/0x3e4
kernel_init+0x34/0x1d0
ret_from_kernel_user_thread+0x14/0x1c
Fixes: b1fc44eaa9ba ("pseries/iommu/ddw: Fix kdump to work in absence of ibm,dma-window")
Signed-off-by: Gaurav Batra <gbatra@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240422205141.10662-1-gbatra@linux.ibm.com
The function inject_data_ue_store() lacks a NULL check for the user
passed values. To prevent below kernel crash include a NULL check.
Call trace:
kstrtoull
kstrtou8
inject_data_ue_store
full_proxy_write
vfs_write
ksys_write
__arm64_sys_write
invoke_syscall
el0_svc_common.constprop.0
do_el0_svc
el0_svc
el0t_64_sync_handler
el0t_64_sync
Fixes: 83bf24051a60 ("EDAC/versal: Make the bit position of injected errors configurable")
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240425121942.26378-3-shubhrajyoti.datta@amd.com
Pull irq fix from Ingo Molnar:
"Fix suspicious RCU usage in __do_softirq()"
* tag 'irq-urgent-2024-05-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
softirq: Fix suspicious RCU usage in __do_softirq()
The syzbot-reported stack trace from hell in this discussion thread
actually has three nested page faults:
https://lore.kernel.org/r/000000000000d5f4fc0616e816d4@google.com
... and I think that's actually the important thing here:
- the first page fault is from user space, and triggers the vsyscall
emulation.
- the second page fault is from __do_sys_gettimeofday(), and that should
just have caused the exception that then sets the return value to
-EFAULT
- the third nested page fault is due to _raw_spin_unlock_irqrestore() ->
preempt_schedule() -> trace_sched_switch(), which then causes a BPF
trace program to run, which does that bpf_probe_read_compat(), which
causes that page fault under pagefault_disable().
It's quite the nasty backtrace, and there's a lot going on.
The problem is literally the vsyscall emulation, which sets
current->thread.sig_on_uaccess_err = 1;
and that causes the fixup_exception() code to send the signal *despite* the
exception being caught.
And I think that is in fact completely bogus. It's completely bogus
exactly because it sends that signal even when it *shouldn't* be sent -
like for the BPF user mode trace gathering.
In other words, I think the whole "sig_on_uaccess_err" thing is entirely
broken, because it makes any nested page-faults do all the wrong things.
Now, arguably, I don't think anybody should enable vsyscall emulation any
more, but this test case clearly does.
I think we should just make the "send SIGSEGV" be something that the
vsyscall emulation does on its own, not this broken per-thread state for
something that isn't actually per thread.
The x86 page fault code actually tried to deal with the "incorrect nesting"
by having that:
if (in_interrupt())
return;
which ignores the sig_on_uaccess_err case when it happens in interrupts,
but as shown by this example, these nested page faults do not need to be
about interrupts at all.
IOW, I think the only right thing is to remove that horrendously broken
code.
The attached patch looks like the ObviouslyCorrect(tm) thing to do.
NOTE! This broken code goes back to this commit in 2011:
4fc3490114bb ("x86-64: Set siginfo and context on vsyscall emulation faults")
... and back then the reason was to get all the siginfo details right.
Honestly, I do not for a moment believe that it's worth getting the siginfo
details right here, but part of the commit says:
This fixes issues with UML when vsyscall=emulate.
... and so my patch to remove this garbage will probably break UML in this
situation.
I do not believe that anybody should be running with vsyscall=emulate in
2024 in the first place, much less if you are doing things like UML. But
let's see if somebody screams.
Reported-and-tested-by: syzbot+83e7f982ca045ab4405c@syzkaller.appspotmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/CAHk-=wh9D6f7HUkDgZHKmDCHUQmp+Co89GP+b8+z+G56BKeyNg@mail.gmail.com
Currently, plpks_confirm_object_flushed() function polls for 5msec in
total instead of 5sec.
Keep max polling time consistent for all the H_CALLs, which take longer
than expected, to be 5sec. Also, make use of fsleep() everywhere to
insert delay.
Reported-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Fixes: 2454a7af0f2a ("powerpc/pseries: define driver for Platform KeyStore")
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240418031230.170954-1-nayna@linux.ibm.com
The NOC errors are not handled in the driver. Remove the request for
registration.
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240425121942.26378-2-shubhrajyoti.datta@amd.com
Pull char/misc driver fixes from Greg KH:
"Here are some small char/misc/other driver fixes and new device ids
for 6.9-rc7 that resolve some reported problems.
Included in here are:
- iio driver fixes
- mei driver fix and new device ids
- dyndbg bugfix
- pvpanic-pci driver bugfix
- slimbus driver bugfix
- fpga new device id
All have been in linux-next with no reported problems"
* tag 'char-misc-6.9-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
slimbus: qcom-ngd-ctrl: Add timeout for wait operation
dyndbg: fix old BUG_ON in >control parser
misc/pvpanic-pci: register attributes via pci_driver
fpga: dfl-pci: add PCI subdevice ID for Intel D5005 card
mei: me: add lunar lake point M DID
mei: pxp: match against PCI_CLASS_DISPLAY_OTHER
iio:imu: adis16475: Fix sync mode setting
iio: accel: mxc4005: Reset chip on probe() and resume()
iio: accel: mxc4005: Interrupt handling fixes
dt-bindings: iio: health: maxim,max30102: fix compatible check
iio: pressure: Fixes SPI support for BMP3xx devices
iio: pressure: Fixes BME280 SPI driver data
Currently, the condition "__this_cpu_read(ksoftirqd) == current" is used to
invoke rcu_softirq_qs() in ksoftirqd tasks context for non-RT kernels.
This works correctly as long as the context is actually task context but
this condition is wrong when:
- the current task is ksoftirqd
- the task is interrupted in a RCU read side critical section
- __do_softirq() is invoked on return from interrupt
Syzkaller triggered the following scenario:
-> finish_task_switch()
-> put_task_struct_rcu_user()
-> call_rcu(&task->rcu, delayed_put_task_struct)
-> __kasan_record_aux_stack()
-> pfn_valid()
-> rcu_read_lock_sched()
<interrupt>
__irq_exit_rcu()
-> __do_softirq)()
-> if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
__this_cpu_read(ksoftirqd) == current)
-> rcu_softirq_qs()
-> RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map))
The rcu quiescent state is reported in the rcu-read critical section, so
the lockdep warning is triggered.
Fix this by splitting out the inner working of __do_softirq() into a helper
function which takes an argument to distinguish between ksoftirqd task
context and interrupted context and invoke it from the relevant call sites
with the proper context information and use that for the conditional
invocation of rcu_softirq_qs().
Reported-by: syzbot+dce04ed6d1438ad69656@syzkaller.appspotmail.com
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240427102808.29356-1-qiang.zhang1211@gmail.com
Link: https://lore.kernel.org/lkml/8f281a10-b85a-4586-9586-5bbc12dc784f@paulmck-laptop/T/#mea8aba4abfcb97bbf499d169ce7f30c4cff1b0e3
With 'iommu=off' on the kernel command line and x2APIC enabled by the BIOS
the code which disables the x2APIC triggers an unchecked MSR access error:
RDMSR from 0x802 at rIP: 0xffffffff94079992 (native_apic_msr_read+0x12/0x50)
This is happens because default_acpi_madt_oem_check() selects an x2APIC
driver before the x2APIC is disabled.
When the x2APIC is disabled because interrupt remapping cannot be enabled
due to 'iommu=off' on the command line, x2apic_disable() invokes
apic_set_fixmap() which in turn tries to read the APIC ID. This triggers
the MSR warning because x2APIC is disabled, but the APIC driver is still
x2APIC based.
Prevent that by adding an argument to apic_set_fixmap() which makes the
APIC ID read out conditional and set it to false from the x2APIC disable
path. That's correct as the APIC ID has already been read out during early
discovery.
Fixes: d10a904435fa ("x86/apic: Consolidate boot_cpu_physical_apicid initialization sites")
Reported-by: Adrian Huang <ahuang12@lenovo.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Adrian Huang <ahuang12@lenovo.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/875xw5t6r7.ffs@tglx
The "close handle without consuming VPD" testcase has inconsistent
results because it fails to initialize the location code object it
passes to ioctl() to create a VPD handle. Initialize the location code
to the empty string as intended.
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Fixes: 9118c5d32bdd ("powerpc/selftests: Add test for papr-vpd")
Reported-by: Geetika Moolchandani <geetika@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240404-papr-vpd-test-uninit-lc-v2-1-37bff46c65a5@linux.ibm.com
README