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Aneesh Kumar K.V e96d9a938e nvdimm/pfn_dev: Prevent the creation of zero-sized namespaces 
On architectures that have different page size values used for kernel
direct mapping and userspace mappings, the user can end up creating zero-sized
namespaces as shown below

:/sys/bus/nd/devices/region1# cat align
0x1000000
/sys/bus/nd/devices/region1# echo 0x200000 > align
/sys/bus/nd/devices/region1/dax1.0# cat supported_alignments
65536 16777216
 $ ndctl create-namespace -r region1 -m devdax -s 18M --align 64K
{
  "dev":"namespace1.0",
  "mode":"devdax",
  "map":"dev",
  "size":0,
  "uuid":"3094329a-0c66-4905-847e-357223e56ab0",
  "daxregion":{
    "id":1,
    "size":0,
    "align":65536
  },
  "align":65536
}
similarily for fsdax

 $ ndctl create-namespace -r region1 -m fsdax  -s 18M --align 64K
{
  "dev":"namespace1.0",
  "mode":"fsdax",
  "map":"dev",
  "size":0,
  "uuid":"45538a6f-dec7-405d-b1da-2a4075e06232",
  "sector_size":512,
  "align":65536,
  "blockdev":"pmem1"
}

In commit 9ffc1d19fc ("mm/memremap_pages: Introduce memremap_compat_align()")
memremap_compat_align was added to make sure the kernel always creates
namespaces with 16MB alignment. But the user can still override the
region alignment and no input validation is done in the region alignment
values to retain the flexibility user had before. However, the kernel
ensures that only part of the namespace that can be mapped via kernel
direct mapping page size is enabled. This is achieved by tracking the
unmapped part of the namespace in pfn_sb->end_trunc. The kernel also
ensures that the start address of the namespace is also aligned to the
kernel direct mapping page size.

Depending on the user request, the kernel implements userspace mapping
alignment by updating pfn device alignment attribute and this value is
used to adjust the start address for userspace mappings. This is tracked
in pfn_sb->dataoff. Hence the available size for userspace mapping is:

usermapping_size = size of the namespace - pfn_sb->end_trun - pfn_sb->dataoff

If the kernel finds the user mapping size zero then don't allow the
creation of namespace.

After fix:
$ ndctl create-namespace -f  -r region1 -m devdax  -s 18M --align 64K
libndctl: ndctl_dax_enable: dax1.1: failed to enable
  Error: namespace1.2: failed to enable

failed to create namespace: No such device or address

And existing zero sized namespace will be marked disabled.
root@ltczz75-lp2:/home/kvaneesh# ndctl  list -N -r region1 -i
[
  {
    "dev":"namespace1.0",
    "mode":"raw",
    "size":18874368,
    "uuid":"94a90fb0-8e78-4fb6-a759-ffc62f9fa181",
    "sector_size":512,
    "state":"disabled"
  },

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Link: https://lore.kernel.org/r/20230809053512.350660-1-aneesh.kumar@linux.ibm.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
History 2023-08-11 09:15:04 -07:00
arch Xtensa fixes for v6.5: 2023-07-16 14:12:49 -07:00
block SCSI fixes on 20230714 2023-07-14 19:57:29 -07:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto crypto: algif_hash - Fix race between MORE and non-MORE sends 2023-07-08 22:48:42 +10:00
Documentation SCSI fixes on 20230714 2023-07-14 19:57:29 -07:00
drivers nvdimm/pfn_dev: Prevent the creation of zero-sized namespaces 2023-08-11 09:15:04 -07:00
fs Five smb3 client fixes 2023-07-16 12:49:05 -07:00
include - Remove a cgroup from under a polling process properly 2023-07-16 13:22:08 -07:00
init Kbuild updates for v6.5 2023-07-01 09:24:31 -07:00
io_uring io_uring-6.5-2023-07-14 2023-07-14 19:46:54 -07:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel - Remove a cgroup from under a polling process properly 2023-07-16 13:22:08 -07:00
lib iov_iter: Mark copy_iovec_from_user() noclone 2023-07-10 09:52:28 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: lock newly mapped VMA with corrected ordering 2023-07-08 16:44:11 -07:00
net A fix to prevent a potential buffer overrun in the messenger, marked 2023-07-14 09:05:15 -07:00
rust rust: error: impl Debug for Error with errname() integration 2023-06-13 01:24:42 +02:00
samples arm64: ftrace: Add direct call trampoline samples support 2023-07-10 17:51:54 -04:00
scripts kallsyms: strip LTO-only suffixes from promoted global functions 2023-07-12 15:39:34 -07:00
security + Bug Fixes 2023-07-07 09:55:31 -07:00
sound sound fixes for 6.5-rc1 2023-07-07 15:40:17 -07:00
tools - Mark copy_iovec_from_user() __noclone in order to prevent gcc from 2023-07-16 13:34:29 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM64: 2023-07-03 15:32:22 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Revert ".gitignore: ignore *.cover and *.mbx" 2023-07-04 15:05:12 -07:00
.mailmap spi: Fixes for v6.5 2023-07-15 08:51:02 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS - Address -Wmissing-prototype warnings 2023-06-26 16:43:54 -07:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS hardening fixes for v6.5-rc2 2023-07-16 12:18:18 -07:00
Makefile Linux 6.5-rc2 2023-07-16 15:10:37 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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.