<feed xmlns='http://www.w3.org/2005/Atom'>
<title>lwn.git/arch/arm64/include/asm, branch docs-5.13</title>
<subtitle>Linux kernel documentation tree maintained by Jonathan Corbet</subtitle>
<id>http://mirrors.hust.edu.cn/git/lwn.git/atom?h=docs-5.13</id>
<link rel='self' href='http://mirrors.hust.edu.cn/git/lwn.git/atom?h=docs-5.13'/>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/'/>
<updated>2021-02-26T18:28:35+00:00</updated>
<entry>
<title>Merge tag 'riscv-for-linus-5.12-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux</title>
<updated>2021-02-26T18:28:35+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2021-02-26T18:28:35+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=8b83369ddcb3fb9cab5c1088987ce477565bb630'/>
<id>urn:sha1:8b83369ddcb3fb9cab5c1088987ce477565bb630</id>
<content type='text'>
Pull RISC-V updates from Palmer Dabbelt:
 "A handful of new RISC-V related patches for this merge window:

   - A check to ensure drivers are properly using uaccess. This isn't
     manifesting with any of the drivers I'm currently using, but may
     catch errors in new drivers.

   - Some preliminary support for the FU740, along with the HiFive
     Unleashed it will appear on.

   - NUMA support for RISC-V, which involves making the arm64 code
     generic.

   - Support for kasan on the vmalloc region.

   - A handful of new drivers for the Kendryte K210, along with the DT
     plumbing required to boot on a handful of K210-based boards.

   - Support for allocating ASIDs.

   - Preliminary support for kernels larger than 128MiB.

   - Various other improvements to our KASAN support, including the
     utilization of huge pages when allocating the KASAN regions.

  We may have already found a bug with the KASAN_VMALLOC code, but it's
  passing my tests. There's a fix in the works, but that will probably
  miss the merge window.

* tag 'riscv-for-linus-5.12-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (75 commits)
  riscv: Improve kasan population by using hugepages when possible
  riscv: Improve kasan population function
  riscv: Use KASAN_SHADOW_INIT define for kasan memory initialization
  riscv: Improve kasan definitions
  riscv: Get rid of MAX_EARLY_MAPPING_SIZE
  soc: canaan: Sort the Makefile alphabetically
  riscv: Disable KSAN_SANITIZE for vDSO
  riscv: Remove unnecessary declaration
  riscv: Add Canaan Kendryte K210 SD card defconfig
  riscv: Update Canaan Kendryte K210 defconfig
  riscv: Add Kendryte KD233 board device tree
  riscv: Add SiPeed MAIXDUINO board device tree
  riscv: Add SiPeed MAIX GO board device tree
  riscv: Add SiPeed MAIX DOCK board device tree
  riscv: Add SiPeed MAIX BiT board device tree
  riscv: Update Canaan Kendryte K210 device tree
  dt-bindings: add resets property to dw-apb-timer
  dt-bindings: fix sifive gpio properties
  dt-bindings: update sifive uart compatible string
  dt-bindings: update sifive clint compatible string
  ...
</content>
</entry>
<entry>
<title>Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux</title>
<updated>2021-02-26T18:19:03+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2021-02-26T18:19:03+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=8f47d753d4ecc6d3e306e22d885d6772625a3423'/>
<id>urn:sha1:8f47d753d4ecc6d3e306e22d885d6772625a3423</id>
<content type='text'>
Pull arm64 fixes from Will Deacon:
 "The big one is a fix for the VHE enabling path during early boot,
  where the code enabling the MMU wasn't necessarily in the identity map
  of the new page-tables, resulting in a consistent crash with 64k
  pages. In fixing that, we noticed some missing barriers too, so we
  added those for the sake of architectural compliance.

  Other than that, just the usual merge window trickle. There'll be more
  to come, too.

  Summary:

   - Fix lockdep false alarm on resume-from-cpuidle path

   - Fix memory leak in kexec_file

   - Fix module linker script to work with GDB

   - Fix error code when trying to use uprobes with AArch32 instructions

   - Fix late VHE enabling with 64k pages

   - Add missing ISBs after TLB invalidation

   - Fix seccomp when tracing syscall -1

   - Fix stacktrace return code at end of stack

   - Fix inconsistent whitespace for pointer return values

   - Fix compiler warnings when building with W=1"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: stacktrace: Report when we reach the end of the stack
  arm64: ptrace: Fix seccomp of traced syscall -1 (NO_SYSCALL)
  arm64: Add missing ISB after invalidating TLB in enter_vhe
  arm64: Add missing ISB after invalidating TLB in __primary_switch
  arm64: VHE: Enable EL2 MMU from the idmap
  KVM: arm64: make the hyp vector table entries local
  arm64/mm: Fixed some coding style issues
  arm64: uprobe: Return EOPNOTSUPP for AARCH32 instruction probing
  kexec: move machine_kexec_post_load() to public interface
  arm64 module: set plt* section addresses to 0x0
  arm64: kexec_file: fix memory leakage in create_dtb() when fdt_open_into() fails
  arm64: spectre: Prevent lockdep splat on v4 mitigation enable path
</content>
</entry>
<entry>
<title>arm64: kasan: simplify and inline MTE functions</title>
<updated>2021-02-26T17:41:03+00:00</updated>
<author>
<name>Andrey Konovalov</name>
<email>andreyknvl@google.com</email>
</author>
<published>2021-02-26T01:20:31+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=2cb34276427a093e2d7cc6ea63ac447bad1ff4c1'/>
<id>urn:sha1:2cb34276427a093e2d7cc6ea63ac447bad1ff4c1</id>
<content type='text'>
This change provides a simpler implementation of mte_get_mem_tag(),
mte_get_random_tag(), and mte_set_mem_tag_range().

Simplifications include removing system_supports_mte() checks as these
functions are onlye called from KASAN runtime that had already checked
system_supports_mte().  Besides that, size and address alignment checks
are removed from mte_set_mem_tag_range(), as KASAN now does those.

This change also moves these functions into the asm/mte-kasan.h header and
implements mte_set_mem_tag_range() via inline assembly to avoid
unnecessary functions calls.

[vincenzo.frascino@arm.com: fix warning in mte_get_random_tag()]
  Link: https://lkml.kernel.org/r/20210211152208.23811-1-vincenzo.frascino@arm.com

Link: https://lkml.kernel.org/r/a26121b294fdf76e369cb7a74351d1c03a908930.1612546384.git.andreyknvl@google.com
Co-developed-by: Vincenzo Frascino &lt;vincenzo.frascino@arm.com&gt;
Signed-off-by: Vincenzo Frascino &lt;vincenzo.frascino@arm.com&gt;
Signed-off-by: Andrey Konovalov &lt;andreyknvl@google.com&gt;
Reviewed-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Cc: Alexander Potapenko &lt;glider@google.com&gt;
Cc: Andrey Ryabinin &lt;aryabinin@virtuozzo.com&gt;
Cc: Branislav Rankov &lt;Branislav.Rankov@arm.com&gt;
Cc: Dmitry Vyukov &lt;dvyukov@google.com&gt;
Cc: Evgenii Stepanov &lt;eugenis@google.com&gt;
Cc: Kevin Brodsky &lt;kevin.brodsky@arm.com&gt;
Cc: Marco Elver &lt;elver@google.com&gt;
Cc: Peter Collingbourne &lt;pcc@google.com&gt;
Cc: Will Deacon &lt;will.deacon@arm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>kfence: use pt_regs to generate stack trace on faults</title>
<updated>2021-02-26T17:41:02+00:00</updated>
<author>
<name>Marco Elver</name>
<email>elver@google.com</email>
</author>
<published>2021-02-26T01:19:08+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=d438fabce7860df3cb9337776be6f90b59ced8ed'/>
<id>urn:sha1:d438fabce7860df3cb9337776be6f90b59ced8ed</id>
<content type='text'>
Instead of removing the fault handling portion of the stack trace based on
the fault handler's name, just use struct pt_regs directly.

Change kfence_handle_page_fault() to take a struct pt_regs, and plumb it
through to kfence_report_error() for out-of-bounds, use-after-free, or
invalid access errors, where pt_regs is used to generate the stack trace.

If the kernel is a DEBUG_KERNEL, also show registers for more information.

Link: https://lkml.kernel.org/r/20201105092133.2075331-1-elver@google.com
Signed-off-by: Marco Elver &lt;elver@google.com&gt;
Suggested-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Acked-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Cc: Alexander Potapenko &lt;glider@google.com&gt;
Cc: Dmitry Vyukov &lt;dvyukov@google.com&gt;
Cc: Jann Horn &lt;jannh@google.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>arm64, kfence: enable KFENCE for ARM64</title>
<updated>2021-02-26T17:41:02+00:00</updated>
<author>
<name>Marco Elver</name>
<email>elver@google.com</email>
</author>
<published>2021-02-26T01:19:03+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=840b239863449f27bf7522deb81e6746fbfbfeaf'/>
<id>urn:sha1:840b239863449f27bf7522deb81e6746fbfbfeaf</id>
<content type='text'>
Add architecture specific implementation details for KFENCE and enable
KFENCE for the arm64 architecture. In particular, this implements the
required interface in &lt;asm/kfence.h&gt;.

KFENCE requires that attributes for pages from its memory pool can
individually be set. Therefore, force the entire linear map to be mapped
at page granularity. Doing so may result in extra memory allocated for
page tables in case rodata=full is not set; however, currently
CONFIG_RODATA_FULL_DEFAULT_ENABLED=y is the default, and the common case
is therefore not affected by this change.

[elver@google.com: add missing copyright and description header]
  Link: https://lkml.kernel.org/r/20210118092159.145934-3-elver@google.com

Link: https://lkml.kernel.org/r/20201103175841.3495947-4-elver@google.com
Signed-off-by: Alexander Potapenko &lt;glider@google.com&gt;
Signed-off-by: Marco Elver &lt;elver@google.com&gt;
Reviewed-by: Dmitry Vyukov &lt;dvyukov@google.com&gt;
Co-developed-by: Alexander Potapenko &lt;glider@google.com&gt;
Reviewed-by: Jann Horn &lt;jannh@google.com&gt;
Reviewed-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Cc: Andrey Konovalov &lt;andreyknvl@google.com&gt;
Cc: Andrey Ryabinin &lt;aryabinin@virtuozzo.com&gt;
Cc: Andy Lutomirski &lt;luto@kernel.org&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Cc: Christopher Lameter &lt;cl@linux.com&gt;
Cc: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Cc: David Rientjes &lt;rientjes@google.com&gt;
Cc: Eric Dumazet &lt;edumazet@google.com&gt;
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Hillf Danton &lt;hdanton@sina.com&gt;
Cc: "H. Peter Anvin" &lt;hpa@zytor.com&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: Joern Engel &lt;joern@purestorage.com&gt;
Cc: Jonathan Corbet &lt;corbet@lwn.net&gt;
Cc: Joonsoo Kim &lt;iamjoonsoo.kim@lge.com&gt;
Cc: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Paul E. McKenney &lt;paulmck@kernel.org&gt;
Cc: Pekka Enberg &lt;penberg@kernel.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: SeongJae Park &lt;sjpark@amazon.de&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Cc: Will Deacon &lt;will@kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>Merge branch 'akpm' (patches from Andrew)</title>
<updated>2021-02-25T00:20:38+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2021-02-25T00:20:38+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=4c48faba5b7f18fb53e4aeeb768932f17c9da1ed'/>
<id>urn:sha1:4c48faba5b7f18fb53e4aeeb768932f17c9da1ed</id>
<content type='text'>
Merge misc updates from Andrew Morton:
 "A few small subsystems and some of MM.

  172 patches.

  Subsystems affected by this patch series: hexagon, scripts, ntfs,
  ocfs2, vfs, and mm (slab-generic, slab, slub, debug, pagecache, swap,
  memcg, pagemap, mprotect, mremap, page-reporting, vmalloc, kasan,
  pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
  mempolicy, oom-kill, hugetlbfs, and migration)"

* emailed patches from Andrew Morton &lt;akpm@linux-foundation.org&gt;: (172 commits)
  mm/migrate: remove unneeded semicolons
  hugetlbfs: remove unneeded return value of hugetlb_vmtruncate()
  hugetlbfs: fix some comment typos
  hugetlbfs: correct some obsolete comments about inode i_mutex
  hugetlbfs: make hugepage size conversion more readable
  hugetlbfs: remove meaningless variable avoid_reserve
  hugetlbfs: correct obsolete function name in hugetlbfs_read_iter()
  hugetlbfs: use helper macro default_hstate in init_hugetlbfs_fs
  hugetlbfs: remove useless BUG_ON(!inode) in hugetlbfs_setattr()
  hugetlbfs: remove special hugetlbfs_set_page_dirty()
  mm/hugetlb: change hugetlb_reserve_pages() to type bool
  mm, oom: fix a comment in dump_task()
  mm/mempolicy: use helper range_in_vma() in queue_pages_test_walk()
  numa balancing: migrate on fault among multiple bound nodes
  mm, compaction: make fast_isolate_freepages() stay within zone
  mm/compaction: fix misbehaviors of fast_find_migrateblock()
  mm/compaction: correct deferral logic for proactive compaction
  mm/compaction: remove duplicated VM_BUG_ON_PAGE !PageLocked
  mm/compaction: remove rcu_read_lock during page compaction
  z3fold: simplify the zhdr initialization code in init_z3fold_page()
  ...
</content>
</entry>
<entry>
<title>kasan, arm64: allow using KUnit tests with HW_TAGS mode</title>
<updated>2021-02-24T21:38:31+00:00</updated>
<author>
<name>Andrey Konovalov</name>
<email>andreyknvl@google.com</email>
</author>
<published>2021-02-24T20:05:26+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=f05842cfb9ae25b5e78c618429c4716d9e4d5fc8'/>
<id>urn:sha1:f05842cfb9ae25b5e78c618429c4716d9e4d5fc8</id>
<content type='text'>
On a high level, this patch allows running KUnit KASAN tests with the
hardware tag-based KASAN mode.

Internally, this change reenables tag checking at the end of each KASAN
test that triggers a tag fault and leads to tag checking being disabled.

Also simplify is_write calculation in report_tag_fault.

With this patch KASAN tests are still failing for the hardware tag-based
mode; fixes come in the next few patches.

[andreyknvl@google.com: export HW_TAGS symbols for KUnit tests]
  Link: https://lkml.kernel.org/r/e7eeb252da408b08f0c81b950a55fb852f92000b.1613155970.git.andreyknvl@google.com

Link: https://linux-review.googlesource.com/id/Id94dc9eccd33b23cda4950be408c27f879e474c8
Link: https://lkml.kernel.org/r/51b23112cf3fd62b8f8e9df81026fa2b15870501.1610733117.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov &lt;andreyknvl@google.com&gt;
Reviewed-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Reviewed-by: Vincenzo Frascino &lt;vincenzo.frascino@arm.com&gt;
Cc: Alexander Potapenko &lt;glider@google.com&gt;
Cc: Andrey Ryabinin &lt;aryabinin@virtuozzo.com&gt;
Cc: Branislav Rankov &lt;Branislav.Rankov@arm.com&gt;
Cc: Dmitry Vyukov &lt;dvyukov@google.com&gt;
Cc: Evgenii Stepanov &lt;eugenis@google.com&gt;
Cc: Kevin Brodsky &lt;kevin.brodsky@arm.com&gt;
Cc: Marco Elver &lt;elver@google.com&gt;
Cc: Peter Collingbourne &lt;pcc@google.com&gt;
Cc: Will Deacon &lt;will.deacon@arm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>Merge tag 'char-misc-5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc</title>
<updated>2021-02-24T18:25:37+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2021-02-24T18:25:37+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=e229b429bb4af24d9828758c0c851bb6a4169400'/>
<id>urn:sha1:e229b429bb4af24d9828758c0c851bb6a4169400</id>
<content type='text'>
Pull char/misc driver updates from Greg KH:
 "Here is the large set of char/misc/whatever driver subsystem updates
  for 5.12-rc1. Over time it seems like this tree is collecting more and
  more tiny driver subsystems in one place, making it easier for those
  maintainers, which is why this is getting larger.

  Included in here are:

   - coresight driver updates

   - habannalabs driver updates

   - virtual acrn driver addition (proper acks from the x86 maintainers)

   - broadcom misc driver addition

   - speakup driver updates

   - soundwire driver updates

   - fpga driver updates

   - amba driver updates

   - mei driver updates

   - vfio driver updates

   - greybus driver updates

   - nvmeem driver updates

   - phy driver updates

   - mhi driver updates

   - interconnect driver udpates

   - fsl-mc bus driver updates

   - random driver fix

   - some small misc driver updates (rtsx, pvpanic, etc.)

  All of these have been in linux-next for a while, with the only
  reported issue being a merge conflict due to the dfl_device_id
  addition from the fpga subsystem in here"

* tag 'char-misc-5.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (311 commits)
  spmi: spmi-pmic-arb: Fix hw_irq overflow
  Documentation: coresight: Add PID tracing description
  coresight: etm-perf: Support PID tracing for kernel at EL2
  coresight: etm-perf: Clarify comment on perf options
  ACRN: update MAINTAINERS: mailing list is subscribers-only
  regmap: sdw-mbq: use MODULE_LICENSE("GPL")
  regmap: sdw: use no_pm routines for SoundWire 1.2 MBQ
  regmap: sdw: use _no_pm functions in regmap_read/write
  soundwire: intel: fix possible crash when no device is detected
  MAINTAINERS: replace my with email with replacements
  mhi: Fix double dma free
  uapi: map_to_7segment: Update example in documentation
  uio: uio_pci_generic: don't fail probe if pdev-&gt;irq equals to IRQ_NOTCONNECTED
  drivers/misc/vmw_vmci: restrict too big queue size in qp_host_alloc_queue
  firewire: replace tricky statement by two simple ones
  vme: make remove callback return void
  firmware: google: make coreboot driver's remove callback return void
  firmware: xilinx: Use explicit values for all enum values
  sample/acrn: Introduce a sample of HSM ioctl interface usage
  virt: acrn: Introduce an interface for Service VM to control vCPU
  ...
</content>
</entry>
<entry>
<title>Merge tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux</title>
<updated>2021-02-23T21:39:45+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2021-02-23T21:39:45+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=7d6beb71da3cc033649d641e1e608713b8220290'/>
<id>urn:sha1:7d6beb71da3cc033649d641e1e608713b8220290</id>
<content type='text'>
Pull idmapped mounts from Christian Brauner:
 "This introduces idmapped mounts which has been in the making for some
  time. Simply put, different mounts can expose the same file or
  directory with different ownership. This initial implementation comes
  with ports for fat, ext4 and with Christoph's port for xfs with more
  filesystems being actively worked on by independent people and
  maintainers.

  Idmapping mounts handle a wide range of long standing use-cases. Here
  are just a few:

   - Idmapped mounts make it possible to easily share files between
     multiple users or multiple machines especially in complex
     scenarios. For example, idmapped mounts will be used in the
     implementation of portable home directories in
     systemd-homed.service(8) where they allow users to move their home
     directory to an external storage device and use it on multiple
     computers where they are assigned different uids and gids. This
     effectively makes it possible to assign random uids and gids at
     login time.

   - It is possible to share files from the host with unprivileged
     containers without having to change ownership permanently through
     chown(2).

   - It is possible to idmap a container's rootfs and without having to
     mangle every file. For example, Chromebooks use it to share the
     user's Download folder with their unprivileged containers in their
     Linux subsystem.

   - It is possible to share files between containers with
     non-overlapping idmappings.

   - Filesystem that lack a proper concept of ownership such as fat can
     use idmapped mounts to implement discretionary access (DAC)
     permission checking.

   - They allow users to efficiently changing ownership on a per-mount
     basis without having to (recursively) chown(2) all files. In
     contrast to chown (2) changing ownership of large sets of files is
     instantenous with idmapped mounts. This is especially useful when
     ownership of a whole root filesystem of a virtual machine or
     container is changed. With idmapped mounts a single syscall
     mount_setattr syscall will be sufficient to change the ownership of
     all files.

   - Idmapped mounts always take the current ownership into account as
     idmappings specify what a given uid or gid is supposed to be mapped
     to. This contrasts with the chown(2) syscall which cannot by itself
     take the current ownership of the files it changes into account. It
     simply changes the ownership to the specified uid and gid. This is
     especially problematic when recursively chown(2)ing a large set of
     files which is commong with the aforementioned portable home
     directory and container and vm scenario.

   - Idmapped mounts allow to change ownership locally, restricting it
     to specific mounts, and temporarily as the ownership changes only
     apply as long as the mount exists.

  Several userspace projects have either already put up patches and
  pull-requests for this feature or will do so should you decide to pull
  this:

   - systemd: In a wide variety of scenarios but especially right away
     in their implementation of portable home directories.

         https://systemd.io/HOME_DIRECTORY/

   - container runtimes: containerd, runC, LXD:To share data between
     host and unprivileged containers, unprivileged and privileged
     containers, etc. The pull request for idmapped mounts support in
     containerd, the default Kubernetes runtime is already up for quite
     a while now: https://github.com/containerd/containerd/pull/4734

   - The virtio-fs developers and several users have expressed interest
     in using this feature with virtual machines once virtio-fs is
     ported.

   - ChromeOS: Sharing host-directories with unprivileged containers.

  I've tightly synced with all those projects and all of those listed
  here have also expressed their need/desire for this feature on the
  mailing list. For more info on how people use this there's a bunch of
  talks about this too. Here's just two recent ones:

      https://www.cncf.io/wp-content/uploads/2020/12/Rootless-Containers-in-Gitpod.pdf
      https://fosdem.org/2021/schedule/event/containers_idmap/

  This comes with an extensive xfstests suite covering both ext4 and
  xfs:

      https://git.kernel.org/brauner/xfstests-dev/h/idmapped_mounts

  It covers truncation, creation, opening, xattrs, vfscaps, setid
  execution, setgid inheritance and more both with idmapped and
  non-idmapped mounts. It already helped to discover an unrelated xfs
  setgid inheritance bug which has since been fixed in mainline. It will
  be sent for inclusion with the xfstests project should you decide to
  merge this.

  In order to support per-mount idmappings vfsmounts are marked with
  user namespaces. The idmapping of the user namespace will be used to
  map the ids of vfs objects when they are accessed through that mount.
  By default all vfsmounts are marked with the initial user namespace.
  The initial user namespace is used to indicate that a mount is not
  idmapped. All operations behave as before and this is verified in the
  testsuite.

  Based on prior discussions we want to attach the whole user namespace
  and not just a dedicated idmapping struct. This allows us to reuse all
  the helpers that already exist for dealing with idmappings instead of
  introducing a whole new range of helpers. In addition, if we decide in
  the future that we are confident enough to enable unprivileged users
  to setup idmapped mounts the permission checking can take into account
  whether the caller is privileged in the user namespace the mount is
  currently marked with.

  The user namespace the mount will be marked with can be specified by
  passing a file descriptor refering to the user namespace as an
  argument to the new mount_setattr() syscall together with the new
  MOUNT_ATTR_IDMAP flag. The system call follows the openat2() pattern
  of extensibility.

  The following conditions must be met in order to create an idmapped
  mount:

   - The caller must currently have the CAP_SYS_ADMIN capability in the
     user namespace the underlying filesystem has been mounted in.

   - The underlying filesystem must support idmapped mounts.

   - The mount must not already be idmapped. This also implies that the
     idmapping of a mount cannot be altered once it has been idmapped.

   - The mount must be a detached/anonymous mount, i.e. it must have
     been created by calling open_tree() with the OPEN_TREE_CLONE flag
     and it must not already have been visible in the filesystem.

  The last two points guarantee easier semantics for userspace and the
  kernel and make the implementation significantly simpler.

  By default vfsmounts are marked with the initial user namespace and no
  behavioral or performance changes are observed.

  The manpage with a detailed description can be found here:

      https://git.kernel.org/brauner/man-pages/c/1d7b902e2875a1ff342e036a9f866a995640aea8

  In order to support idmapped mounts, filesystems need to be changed
  and mark themselves with the FS_ALLOW_IDMAP flag in fs_flags. The
  patches to convert individual filesystem are not very large or
  complicated overall as can be seen from the included fat, ext4, and
  xfs ports. Patches for other filesystems are actively worked on and
  will be sent out separately. The xfstestsuite can be used to verify
  that port has been done correctly.

  The mount_setattr() syscall is motivated independent of the idmapped
  mounts patches and it's been around since July 2019. One of the most
  valuable features of the new mount api is the ability to perform
  mounts based on file descriptors only.

  Together with the lookup restrictions available in the openat2()
  RESOLVE_* flag namespace which we added in v5.6 this is the first time
  we are close to hardened and race-free (e.g. symlinks) mounting and
  path resolution.

  While userspace has started porting to the new mount api to mount
  proper filesystems and create new bind-mounts it is currently not
  possible to change mount options of an already existing bind mount in
  the new mount api since the mount_setattr() syscall is missing.

  With the addition of the mount_setattr() syscall we remove this last
  restriction and userspace can now fully port to the new mount api,
  covering every use-case the old mount api could. We also add the
  crucial ability to recursively change mount options for a whole mount
  tree, both removing and adding mount options at the same time. This
  syscall has been requested multiple times by various people and
  projects.

  There is a simple tool available at

      https://github.com/brauner/mount-idmapped

  that allows to create idmapped mounts so people can play with this
  patch series. I'll add support for the regular mount binary should you
  decide to pull this in the following weeks:

  Here's an example to a simple idmapped mount of another user's home
  directory:

	u1001@f2-vm:/$ sudo ./mount --idmap both:1000:1001:1 /home/ubuntu/ /mnt

	u1001@f2-vm:/$ ls -al /home/ubuntu/
	total 28
	drwxr-xr-x 2 ubuntu ubuntu 4096 Oct 28 22:07 .
	drwxr-xr-x 4 root   root   4096 Oct 28 04:00 ..
	-rw------- 1 ubuntu ubuntu 3154 Oct 28 22:12 .bash_history
	-rw-r--r-- 1 ubuntu ubuntu  220 Feb 25  2020 .bash_logout
	-rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25  2020 .bashrc
	-rw-r--r-- 1 ubuntu ubuntu  807 Feb 25  2020 .profile
	-rw-r--r-- 1 ubuntu ubuntu    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ ls -al /mnt/
	total 28
	drwxr-xr-x  2 u1001 u1001 4096 Oct 28 22:07 .
	drwxr-xr-x 29 root  root  4096 Oct 28 22:01 ..
	-rw-------  1 u1001 u1001 3154 Oct 28 22:12 .bash_history
	-rw-r--r--  1 u1001 u1001  220 Feb 25  2020 .bash_logout
	-rw-r--r--  1 u1001 u1001 3771 Feb 25  2020 .bashrc
	-rw-r--r--  1 u1001 u1001  807 Feb 25  2020 .profile
	-rw-r--r--  1 u1001 u1001    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw-------  1 u1001 u1001 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ touch /mnt/my-file

	u1001@f2-vm:/$ setfacl -m u:1001:rwx /mnt/my-file

	u1001@f2-vm:/$ sudo setcap -n 1001 cap_net_raw+ep /mnt/my-file

	u1001@f2-vm:/$ ls -al /mnt/my-file
	-rw-rwxr--+ 1 u1001 u1001 0 Oct 28 22:14 /mnt/my-file

	u1001@f2-vm:/$ ls -al /home/ubuntu/my-file
	-rw-rwxr--+ 1 ubuntu ubuntu 0 Oct 28 22:14 /home/ubuntu/my-file

	u1001@f2-vm:/$ getfacl /mnt/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: mnt/my-file
	# owner: u1001
	# group: u1001
	user::rw-
	user:u1001:rwx
	group::rw-
	mask::rwx
	other::r--

	u1001@f2-vm:/$ getfacl /home/ubuntu/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: home/ubuntu/my-file
	# owner: ubuntu
	# group: ubuntu
	user::rw-
	user:ubuntu:rwx
	group::rw-
	mask::rwx
	other::r--"

* tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: (41 commits)
  xfs: remove the possibly unused mp variable in xfs_file_compat_ioctl
  xfs: support idmapped mounts
  ext4: support idmapped mounts
  fat: handle idmapped mounts
  tests: add mount_setattr() selftests
  fs: introduce MOUNT_ATTR_IDMAP
  fs: add mount_setattr()
  fs: add attr_flags_to_mnt_flags helper
  fs: split out functions to hold writers
  namespace: only take read lock in do_reconfigure_mnt()
  mount: make {lock,unlock}_mount_hash() static
  namespace: take lock_mount_hash() directly when changing flags
  nfs: do not export idmapped mounts
  overlayfs: do not mount on top of idmapped mounts
  ecryptfs: do not mount on top of idmapped mounts
  ima: handle idmapped mounts
  apparmor: handle idmapped mounts
  fs: make helpers idmap mount aware
  exec: handle idmapped mounts
  would_dump: handle idmapped mounts
  ...
</content>
</entry>
<entry>
<title>Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm</title>
<updated>2021-02-21T21:31:43+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2021-02-21T21:31:43+00:00</published>
<link rel='alternate' type='text/html' href='http://mirrors.hust.edu.cn/git/lwn.git/commit/?id=3e10585335b7967326ca7b4118cada0d2d00a2ab'/>
<id>urn:sha1:3e10585335b7967326ca7b4118cada0d2d00a2ab</id>
<content type='text'>
Pull KVM updates from Paolo Bonzini:
 "x86:

   - Support for userspace to emulate Xen hypercalls

   - Raise the maximum number of user memslots

   - Scalability improvements for the new MMU.

     Instead of the complex "fast page fault" logic that is used in
     mmu.c, tdp_mmu.c uses an rwlock so that page faults are concurrent,
     but the code that can run against page faults is limited. Right now
     only page faults take the lock for reading; in the future this will
     be extended to some cases of page table destruction. I hope to
     switch the default MMU around 5.12-rc3 (some testing was delayed
     due to Chinese New Year).

   - Cleanups for MAXPHYADDR checks

   - Use static calls for vendor-specific callbacks

   - On AMD, use VMLOAD/VMSAVE to save and restore host state

   - Stop using deprecated jump label APIs

   - Workaround for AMD erratum that made nested virtualization
     unreliable

   - Support for LBR emulation in the guest

   - Support for communicating bus lock vmexits to userspace

   - Add support for SEV attestation command

   - Miscellaneous cleanups

  PPC:

   - Support for second data watchpoint on POWER10

   - Remove some complex workarounds for buggy early versions of POWER9

   - Guest entry/exit fixes

  ARM64:

   - Make the nVHE EL2 object relocatable

   - Cleanups for concurrent translation faults hitting the same page

   - Support for the standard TRNG hypervisor call

   - A bunch of small PMU/Debug fixes

   - Simplification of the early init hypercall handling

  Non-KVM changes (with acks):

   - Detection of contended rwlocks (implemented only for qrwlocks,
     because KVM only needs it for x86)

   - Allow __DISABLE_EXPORTS from assembly code

   - Provide a saner follow_pfn replacements for modules"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (192 commits)
  KVM: x86/xen: Explicitly pad struct compat_vcpu_info to 64 bytes
  KVM: selftests: Don't bother mapping GVA for Xen shinfo test
  KVM: selftests: Fix hex vs. decimal snafu in Xen test
  KVM: selftests: Fix size of memslots created by Xen tests
  KVM: selftests: Ignore recently added Xen tests' build output
  KVM: selftests: Add missing header file needed by xAPIC IPI tests
  KVM: selftests: Add operand to vmsave/vmload/vmrun in svm.c
  KVM: SVM: Make symbol 'svm_gp_erratum_intercept' static
  locking/arch: Move qrwlock.h include after qspinlock.h
  KVM: PPC: Book3S HV: Fix host radix SLB optimisation with hash guests
  KVM: PPC: Book3S HV: Ensure radix guest has no SLB entries
  KVM: PPC: Don't always report hash MMU capability for P9 &lt; DD2.2
  KVM: PPC: Book3S HV: Save and restore FSCR in the P9 path
  KVM: PPC: remove unneeded semicolon
  KVM: PPC: Book3S HV: Use POWER9 SLBIA IH=6 variant to clear SLB
  KVM: PPC: Book3S HV: No need to clear radix host SLB before loading HPT guest
  KVM: PPC: Book3S HV: Fix radix guest SLB side channel
  KVM: PPC: Book3S HV: Remove support for running HPT guest on RPT host without mixed mode support
  KVM: PPC: Book3S HV: Introduce new capability for 2nd DAWR
  KVM: PPC: Book3S HV: Add infrastructure to support 2nd DAWR
  ...
</content>
</entry>
</feed>
