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Linux kernel
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This reverts commits 4bad58ebc8bc4f20d89cff95417c9b4674769709 (and
399f8dd9a866e107639eabd3c1979cd526ca3a98, which tried to fix it).
I do not believe these are correct, and I'm about to release 5.13, so am
reverting them out of an abundance of caution.
The locking is odd, and appears broken.
On the allocation side (in __sigqueue_alloc()), the locking is somewhat
straightforward: it depends on sighand->siglock. Since one caller
doesn't hold that lock, it further then tests 'sigqueue_flags' to avoid
the case with no locks held.
On the freeing side (in sigqueue_cache_or_free()), there is no locking
at all, and the logic instead depends on 'current' being a single
thread, and not able to race with itself.
To make things more exciting, there's also the data race between freeing
a signal and allocating one, which is handled by using WRITE_ONCE() and
READ_ONCE(), and being mutually exclusive wrt the initial state (ie
freeing will only free if the old state was NULL, while allocating will
obviously only use the value if it was non-NULL, so only one or the
other will actually act on the value).
However, while the free->alloc paths do seem mutually exclusive thanks
to just the data value dependency, it's not clear what the memory
ordering constraints are on it. Could writes from the previous
allocation possibly be delayed and seen by the new allocation later,
causing logical inconsistencies?
So it's all very exciting and unusual.
And in particular, it seems that the freeing side is incorrect in
depending on "current" being single-threaded. Yes, 'current' is a
single thread, but in the presense of asynchronous events even a single
thread can have data races.
And such asynchronous events can and do happen, with interrupts causing
signals to be flushed and thus free'd (for example - sending a
SIGCONT/SIGSTOP can happen from interrupt context, and can flush
previously queued process control signals).
So regardless of all the other questions about the memory ordering and
locking for this new cached allocation, the sigqueue_cache_or_free()
assumptions seem to be fundamentally incorrect.
It may be that people will show me the errors of my ways, and tell me
why this is all safe after all. We can reinstate it if so. But my
current belief is that the WRITE_ONCE() that sets the cached entry needs
to be a smp_store_release(), and the READ_ONCE() that finds a cached
entry needs to be a smp_load_acquire() to handle memory ordering
correctly.
And the sequence in sigqueue_cache_or_free() would need to either use a
lock or at least be interrupt-safe some way (perhaps by using something
like the percpu 'cmpxchg': it doesn't need to be SMP-safe, but like the
percpu operations it needs to be interrupt-safe).
Fixes: 399f8dd9a866 ("signal: Prevent sigqueue caching after task got released")
Fixes: 4bad58ebc8bc ("signal: Allow tasks to cache one sigqueue struct")
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull s390 fixes from Vasily Gorbik:
- Fix a couple of late pt_regs flags handling findings of conversion to
generic entry.
- Fix potential register clobbering in stack switch helper.
- Fix thread/group masks for offline cpus.
- Fix cleanup of mdev resources when remove callback is invoked in
vfio-ap code.
* tag 's390-5.13-5' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
s390/stack: fix possible register corruption with stack switch helper
s390/topology: clear thread/group maps for offline cpus
s390/vfio-ap: clean up mdev resources when remove callback invoked
s390: clear pt_regs::flags on irq entry
s390: fix system call restart with multiple signals
Pull pin control fixes from Linus Walleij:
"Two last-minute fixes:
- Put an fwnode in the errorpath in the SGPIO driver
- Fix the number of GPIO lines per bank in the STM32 driver"
* tag 'pinctrl-v5.13-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
pinctrl: stm32: fix the reported number of GPIO lines per bank
pinctrl: microchip-sgpio: Put fwnode in error case during ->probe()
The CALL_ON_STACK macro is used to call a C function from inline
assembly, and therefore must consider the C ABI, which says that only
registers 6-13, and 15 are non-volatile (restored by the called
function).
The inline assembly incorrectly marks all registers used to pass
parameters to the called function as read-only input operands, instead
of operands that are read and written to. This might result in
register corruption depending on usage, compiler, and compile options.
Fix this by marking all operands used to pass parameters as read/write
operands. To keep the code simple even register 6, if used, is marked
as read-write operand.
Fixes: ff340d2472ec ("s390: add stack switch helper")
Cc: <stable@kernel.org> # 4.20
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Pull SCSI fixes from James Bottomley:
"Two small fixes, both in upper layer drivers (scsi disk and cdrom).
The sd one is fixing a commit changing revalidation that came from the
block tree a while ago (5.10) and the sr one adds handling of a
condition we didn't previously handle for manually removed media"
* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: sd: Call sd_revalidate_disk() for ioctl(BLKRRPART)
scsi: sr: Return appropriate error code when disk is ejected
Each GPIO bank supports a variable number of lines which is usually 16, but
is less in some cases : this is specified by the last argument of the
"gpio-ranges" bank node property.
Report to the framework, the actual number of lines, so the libgpiod
gpioinfo command lists the actually existing GPIO lines.
Fixes: 1dc9d289154b ("pinctrl: stm32: add possibility to use gpio-ranges to declare bank range")
Signed-off-by: Fabien Dessenne <fabien.dessenne@foss.st.com>
Link: https://lore.kernel.org/r/20210617144629.2557693-1-fabien.dessenne@foss.st.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
The current code doesn't clear the thread/group maps for offline
CPUs. This may cause kernel crashes like the one bewlow in common
code that assumes if a CPU has sibblings it is online.
Unable to handle kernel pointer dereference in virtual kernel address space
Call Trace:
[<000000013a4b8c3c>] blk_mq_map_swqueue+0x10c/0x388
([<000000013a4b8bcc>] blk_mq_map_swqueue+0x9c/0x388)
[<000000013a4b9300>] blk_mq_init_allocated_queue+0x448/0x478
[<000000013a4b9416>] blk_mq_init_queue+0x4e/0x90
[<000003ff8019d3e6>] loop_add+0x106/0x278 [loop]
[<000003ff801b8148>] loop_init+0x148/0x1000 [loop]
[<0000000139de4924>] do_one_initcall+0x3c/0x1e0
[<0000000139ef449a>] do_init_module+0x6a/0x2a0
[<0000000139ef61bc>] __do_sys_finit_module+0xa4/0xc0
[<0000000139de9e6e>] do_syscall+0x7e/0xd0
[<000000013a8e0aec>] __do_syscall+0xbc/0x110
[<000000013a8ee2e8>] system_call+0x78/0xa0
Fixes: 52aeda7accb6 ("s390/topology: remove offline CPUs from CPU topology masks")
Cc: <stable@kernel.org> # 5.7+
Reported-by: Marius Hillenbrand <mhillen@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Merge misc fixes from Andrew Morton:
"24 patches, based on 4a09d388f2ab382f217a764e6a152b3f614246f6.
Subsystems affected by this patch series: mm (thp, vmalloc, hugetlb,
memory-failure, and pagealloc), nilfs2, kthread, MAINTAINERS, and
mailmap"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (24 commits)
mailmap: add Marek's other e-mail address and identity without diacritics
MAINTAINERS: fix Marek's identity again
mm/page_alloc: do bulk array bounds check after checking populated elements
mm/page_alloc: __alloc_pages_bulk(): do bounds check before accessing array
mm/hwpoison: do not lock page again when me_huge_page() successfully recovers
mm,hwpoison: return -EHWPOISON to denote that the page has already been poisoned
mm/memory-failure: use a mutex to avoid memory_failure() races
mm, futex: fix shared futex pgoff on shmem huge page
kthread: prevent deadlock when kthread_mod_delayed_work() races with kthread_cancel_delayed_work_sync()
kthread_worker: split code for canceling the delayed work timer
mm/vmalloc: unbreak kasan vmalloc support
KVM: s390: prepare for hugepage vmalloc
mm/vmalloc: add vmalloc_no_huge
nilfs2: fix memory leak in nilfs_sysfs_delete_device_group
mm/thp: another PVMW_SYNC fix in page_vma_mapped_walk()
mm/thp: fix page_vma_mapped_walk() if THP mapped by ptes
mm: page_vma_mapped_walk(): get vma_address_end() earlier
mm: page_vma_mapped_walk(): use goto instead of while (1)
mm: page_vma_mapped_walk(): add a level of indentation
mm: page_vma_mapped_walk(): crossing page table boundary
...
While the disk state has nothing to do with partitions, BLKRRPART is used
to force a full revalidate after things like a disk format for historical
reasons. Restore that behavior.
Link: https://lore.kernel.org/r/20210617115504.1732350-1-hch@lst.de
Fixes: 471bd0af544b ("sd: use bdev_check_media_change")
Reported-by: Xiang Chen <chenxiang66@hisilicon.com>
Tested-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
device_for_each_child_node() bumps a reference counting of a returned variable.
We have to balance it whenever we return to the caller.
Fixes: 7e5ea974e61c ("pinctrl: pinctrl-microchip-sgpio: Add pinctrl driver for Microsemi Serial GPIO")
Cc: Lars Povlsen <lars.povlsen@microchip.com>
Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210606191940.29312-1-andy.shevchenko@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
The mdev remove callback for the vfio_ap device driver bails out with
-EBUSY if the mdev is in use by a KVM guest (i.e., the KVM pointer in the
struct ap_matrix_mdev is not NULL). The intended purpose was
to prevent the mdev from being removed while in use. There are two
problems with this scenario:
1. Returning a non-zero return code from the remove callback does not
prevent the removal of the mdev.
2. The KVM pointer in the struct ap_matrix_mdev will always be NULL because
the remove callback will not get invoked until the mdev fd is closed.
When the mdev fd is closed, the mdev release callback is invoked and
clears the KVM pointer from the struct ap_matrix_mdev.
Let's go ahead and remove the check for KVM in the remove callback and
allow the cleanup of mdev resources to proceed.
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20210609224634.575156-2-akrowiak@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This ioctl request reads from uffdio_continue structure written by
userspace which justifies _IOC_WRITE flag. It also writes back to that
structure which justifies _IOC_READ flag.
See NOTEs in include/uapi/asm-generic/ioctl.h for more information.
Fixes: f619147104c8 ("userfaultfd: add UFFDIO_CONTINUE ioctl")
Signed-off-by: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some of my commits were sent with identities
Marek Behun <marek.behun@nic.cz>
Marek Behún <marek.behun@nic.cz>
while the correct one is
Marek Behún <kabel@kernel.org>
Put this into mailmap so that git shortlog prints all my commits under
one identity.
Link: https://lkml.kernel.org/r/20210616113624.19351-2-kabel@kernel.org
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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