sg_miter_stop() checks for disabled preemption before unmapping a page
via kunmap_atomic(). The kernel doc mentions under context that
preemption must be disabled if SG_MITER_ATOMIC is set.
There is no active requirement for the caller to have preemption
disabled before invoking sg_mitter_stop(). The sg_mitter_*()
implementation itself has no such requirement.
In fact, preemption is disabled by kmap_atomic() as part of
sg_miter_next() and remains disabled as long as there is an active
SG_MITER_ATOMIC mapping. This is a consequence of kmap_atomic() and not
a requirement for sg_mitter_*() itself.
The user chooses SG_MITER_ATOMIC because it uses the API in a context
where blocking is not possible or blocking is possible but he chooses a
lower weight mapping which is not available on all CPUs and so it might
need less overhead to setup at a price that now preemption will be
disabled.
The kmap_atomic() implementation on PREEMPT_RT does not disable
preemption. It simply disables CPU migration to ensure that the task
remains on the same CPU while the caller remains preemptible. This in
turn triggers the warning in sg_miter_stop() because preemption is
allowed.
The PREEMPT_RT and !PREEMPT_RT implementation of kmap_atomic() disable
pagefaults as a requirement. It is sufficient to check for this instead
of disabled preemption.
Check for disabled pagefault handler in the SG_MITER_ATOMIC case.
Remove the "preemption disabled" part from the kernel doc as the
sg_milter*() implementation does not care.
[bigeasy@linutronix.de: commit description]
Link: https://lkml.kernel.org/r/20211015211409.cqopacv3pxdwn2ty@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have observed that on very large machines with newer CPUs, the static
key/branch switching delay is on the order of milliseconds. This is due
to the required broadcast IPIs, which simply does not scale well to
hundreds of CPUs (cores). If done too frequently, this can adversely
affect tail latencies of various workloads.
One workaround is to increase the sample interval to several seconds,
while decreasing sampled allocation coverage, but the problem still
exists and could still increase tail latencies.
As already noted in the Kconfig help text, there are trade-offs: at
lower sample intervals the dynamic branch results in better performance;
however, at very large sample intervals, the static keys mode can result
in better performance -- careful benchmarking is recommended.
Our initial benchmarking showed that with large enough sample intervals
and workloads stressing the allocator, the static keys mode was slightly
better. Evaluating and observing the possible system-wide side-effects
of the static-key-switching induced broadcast IPIs, however, was a blind
spot (in particular on large machines with 100s of cores).
Therefore, a major downside of the static keys mode is, unfortunately,
that it is hard to predict performance on new system architectures and
topologies, but also making conclusions about performance of new
workloads based on a limited set of benchmarks.
Most distributions will simply select the defaults, while targeting a
large variety of different workloads and system architectures. As such,
the better default is CONFIG_KFENCE_STATIC_KEYS=n, and re-enabling it is
only recommended after careful evaluation.
For reference, on x86-64 the condition in kfence_alloc() generates
exactly
2 instructions in the kmem_cache_alloc() fast-path:
| ...
| cmpl $0x0,0x1a8021c(%rip) # ffffffff82d560d0 <kfence_allocation_gate>
| je ffffffff812d6003 <kmem_cache_alloc+0x243>
| ...
which, given kfence_allocation_gate is infrequently modified, should be
well predicted by most CPUs.
Link: https://lkml.kernel.org/r/20211019102524.2807208-2-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
filter_irq_stacks() has little to do with the stackdepot implementation,
except that it is usually used by users (such as KASAN) of stackdepot to
reduce the stack trace.
However, filter_irq_stacks() itself is not useful without a stack trace
as obtained by stack_trace_save() and friends.
Therefore, move filter_irq_stacks() to kernel/stacktrace.c, so that new
users of filter_irq_stacks() do not have to start depending on
STACKDEPOT only for filter_irq_stacks().
Link: https://lkml.kernel.org/r/20210923104803.2620285-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Aleksandr Nogikh <nogikh@google.com>
Cc: Taras Madan <tarasmadan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With HW tag-based KASAN, error checks are performed implicitly by the
load and store instructions in the memcpy implementation. A failed
check results in tag checks being disabled and execution will keep
going. As a result, under HW tag-based KASAN, prior to commit
1b0668be62 ("kasan: test: disable kmalloc_memmove_invalid_size for
HW_TAGS"), this memcpy would end up corrupting memory until it hits an
inaccessible page and causes a kernel panic.
This is a pre-existing issue that was revealed by commit 285133040e
("arm64: Import latest memcpy()/memmove() implementation") which changed
the memcpy implementation from using signed comparisons (incorrectly,
resulting in the memcpy being terminated early for negative sizes) to
using unsigned comparisons.
It is unclear how this could be handled by memcpy itself in a reasonable
way. One possibility would be to add an exception handler that would
force memcpy to return if a tag check fault is detected -- this would
make the behavior roughly similar to generic and SW tag-based KASAN.
However, this wouldn't solve the problem for asynchronous mode and also
makes memcpy behavior inconsistent with manually copying data.
This test was added as a part of a series that taught KASAN to detect
negative sizes in memory operations, see commit 8cceeff48f ("kasan:
detect negative size in memory operation function"). Therefore we
should keep testing for negative sizes with generic and SW tag-based
KASAN. But there is some value in testing small memcpy overflows, so
let's add another test with memcpy that does not destabilize the kernel
by performing out-of-bounds writes, and run it in all modes.
Link: https://linux-review.googlesource.com/id/I048d1e6a9aff766c4a53f989fb0c83de68923882
Link: https://lkml.kernel.org/r/20210910211356.3603758-1-pcc@google.com
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull Kunit fixes from Shuah Khan:
- Fixes to address the structleak plugin causing the stack frame size
to grow immensely when used with KUnit. Fixes include adding a new
makefile to disable structleak and using it from KUnit iio, device
property, thunderbolt, and bitfield tests to disable it.
- KUnit framework reference count leak in kfree_at_end
- KUnit tool fix to resolve conflict between --json and --raw_output
and generate correct test output in either case.
- kernel-doc warnings due to mismatched arg names
* tag 'linux-kselftest-kunit-fixes-5.15-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
kunit: fix kernel-doc warnings due to mismatched arg names
bitfield: build kunit tests without structleak plugin
thunderbolt: build kunit tests without structleak plugin
device property: build kunit tests without structleak plugin
iio/test-format: build kunit tests without structleak plugin
gcc-plugins/structleak: add makefile var for disabling structleak
kunit: fix reference count leak in kfree_at_end
kunit: tool: better handling of quasi-bool args (--json, --raw_output)
The structleak plugin causes the stack frame size to grow immensely:
lib/bitfield_kunit.c: In function 'test_bitfields_constants':
lib/bitfield_kunit.c:93:1: error: the frame size of 7440 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
Turn it off in this file.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
The reference counting issue happens in the normal path of
kfree_at_end(). When kunit_alloc_and_get_resource() is invoked, the
function forgets to handle the returned resource object, whose refcount
increased inside, causing a refcount leak.
Fix this issue by calling kunit_alloc_resource() instead of
kunit_alloc_and_get_resource().
Fixed the following when applying:
Shuah Khan <skhan@linuxfoundation.org>
CHECK: Alignment should match open parenthesis
+ kunit_alloc_resource(test, NULL, kfree_res_free, GFP_KERNEL,
(void *)to_free);
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Reviewed-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Pull networking fixes from Jakub Kicinski:
"Current release - regressions:
- dsa: bcm_sf2: fix array overrun in bcm_sf2_num_active_ports()
Previous releases - regressions:
- introduce a shutdown method to mdio device drivers, and make DSA
switch drivers compatible with masters disappearing on shutdown;
preventing infinite reference wait
- fix issues in mdiobus users related to ->shutdown vs ->remove
- virtio-net: fix pages leaking when building skb in big mode
- xen-netback: correct success/error reporting for the
SKB-with-fraglist
- dsa: tear down devlink port regions when tearing down the devlink
port on error
- nexthop: fix division by zero while replacing a resilient group
- hns3: check queue, vf, vlan ids range before using
Previous releases - always broken:
- napi: fix race against netpoll causing NAPI getting stuck
- mlx4_en: ensure link operstate is updated even if link comes up
before netdev registration
- bnxt_en: fix TX timeout when TX ring size is set to the smallest
- enetc: fix illegal access when reading affinity_hint; prevent oops
on sysfs access
- mtk_eth_soc: avoid creating duplicate offload entries
Misc:
- core: correct the sock::sk_lock.owned lockdep annotations"
* tag 'net-5.15-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (51 commits)
atlantic: Fix issue in the pm resume flow.
net/mlx4_en: Don't allow aRFS for encapsulated packets
net: mscc: ocelot: fix forwarding from BLOCKING ports remaining enabled
net: ethernet: mtk_eth_soc: avoid creating duplicate offload entries
nfc: st-nci: Add SPI ID matching DT compatible
MAINTAINERS: remove Guvenc Gulce as net/smc maintainer
nexthop: Fix memory leaks in nexthop notification chain listeners
mptcp: ensure tx skbs always have the MPTCP ext
qed: rdma - don't wait for resources under hw error recovery flow
s390/qeth: fix deadlock during failing recovery
s390/qeth: Fix deadlock in remove_discipline
s390/qeth: fix NULL deref in qeth_clear_working_pool_list()
net: dsa: realtek: register the MDIO bus under devres
net: dsa: don't allocate the slave_mii_bus using devres
Doc: networking: Fox a typo in ice.rst
net: dsa: fix dsa_tree_setup error path
net/smc: fix 'workqueue leaked lock' in smc_conn_abort_work
net/smc: add missing error check in smc_clc_prfx_set()
net: hns3: fix a return value error in hclge_get_reset_status()
net: hns3: check vlan id before using it
...
Nathan Chancellor reports that the recent change to pci_iounmap in
commit 9caea00076 ("parisc: Declare pci_iounmap() parisc version only
when CONFIG_PCI enabled") causes build errors on arm64.
It took me about two hours to convince myself that I think I know what
the logic of that mess of #ifdef's in the <asm-generic/io.h> header file
really aim to do, and rewrite it to be easier to follow.
Famous last words.
Anyway, the code has now been lifted from that grotty header file into
lib/pci_iomap.c, and has fairly extensive comments about what the logic
is. It also avoids indirecting through another confusing (and badly
named) helper function that has other preprocessor config conditionals.
Let's see what odd architecture did something else strange in this area
to break things. But my arm64 cross build is clean.
Fixes: 9caea00076 ("parisc: Declare pci_iounmap() parisc version only when CONFIG_PCI enabled")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Ulrich Teichert <krypton@ulrich-teichert.org>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull io_uring iov_iter retry fixes from Jens Axboe:
"This adds a helper to save/restore iov_iter state, and modifies
io_uring to use it.
After that is done, we can now kill the iter->truncated addition that
we added for this release. The io_uring change is being overly
cautious with the save/restore/advance, but better safe than sorry and
we can always improve that and reduce the overhead if it proves to be
of concern. The only case to be worried about in this regard is huge
IO, where iteration can take a while to iterate segments.
I spent some time writing test cases, and expanded the coverage quite
a bit from the last posting of this. liburing carries this regression
test case now:
https://git.kernel.dk/cgit/liburing/tree/test/file-verify.c
which exercises all of this. It now also supports provided buffers,
and explicitly tests for end-of-file/device truncation as well.
On top of that, Pavel sanitized the IOPOLL retry path to follow the
exact same pattern as normal IO"
* tag 'iov_iter.3-5.15-2021-09-17' of git://git.kernel.dk/linux-block:
io_uring: move iopoll reissue into regular IO path
Revert "iov_iter: track truncated size"
io_uring: use iov_iter state save/restore helpers
iov_iter: add helper to save iov_iter state
