drivers/char: remove /dev/kmem for good

Patch series "drivers/char: remove /dev/kmem for good".

Exploring /dev/kmem and /dev/mem in the context of memory hot(un)plug and
memory ballooning, I starte

drivers/char: remove /dev/kmem for good

Patch series "drivers/char: remove /dev/kmem for good".

Exploring /dev/kmem and /dev/mem in the context of memory hot(un)plug and
memory ballooning, I started questioning the existence of /dev/kmem.

Comparing it with the /proc/kcore implementation, it does not seem to be
able to deal with things like

a) Pages unmapped from the direct mapping (e.g., to be used by secretmem)
-> kern_addr_valid(). virt_addr_valid() is not sufficient.

b) Special cases like gart aperture memory that is not to be touched
-> mem_pfn_is_ram()

Unless I am missing something, it's at least broken in some cases and might
fault/crash the machine.

Looks like its existence has been questioned before in 2005 and 2010 [1],
after ~11 additional years, it might make sense to revive the discussion.

CONFIG_DEVKMEM is only enabled in a single defconfig (on purpose or by
mistake?). All distributions disable it: in Ubuntu it has been disabled
for more than 10 years, in Debian since 2.6.31, in Fedora at least
starting with FC3, in RHEL starting with RHEL4, in SUSE starting from
15sp2, and OpenSUSE has it disabled as well.

1) /dev/kmem was popular for rootkits [2] before it got disabled
basically everywhere. Ubuntu documents [3] "There is no modern user of
/dev/kmem any more beyond attackers using it to load kernel rootkits.".
RHEL documents in a BZ [5] "it served no practical purpose other than to
serve as a potential security problem or to enable binary module drivers
to access structures/functions they shouldn't be touching"

2) /proc/kcore is a decent interface to have a controlled way to read
kernel memory for debugging puposes. (will need some extensions to
deal with memory offlining/unplug, memory ballooning, and poisoned
pages, though)

3) It might be useful for corner case debugging [1]. KDB/KGDB might be a
better fit, especially, to write random memory; harder to shoot
yourself into the foot.

4) "Kernel Memory Editor" [4] hasn't seen any updates since 2000 and seems
to be incompatible with 64bit [1]. For educational purposes,
/proc/kcore might be used to monitor value updates -- or older
kernels can be used.

5) It's broken on arm64, and therefore, completely disabled there.

Looks like it's essentially unused and has been replaced by better
suited interfaces for individual tasks (/proc/kcore, KDB/KGDB). Let's
just remove it.

[1] https://lwn.net/Articles/147901/
[2] https://www.linuxjournal.com/article/10505
[3] https://wiki.ubuntu.com/Security/Features#A.2Fdev.2Fkmem_disabled
[4] https://sourceforge.net/projects/kme/
[5] https://bugzilla.redhat.com/show_bug.cgi?id=154796

Link: https://lkml.kernel.org/r/20210324102351.6932-1-david@redhat.com
Link: https://lkml.kernel.org/r/20210324102351.6932-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Alexander A. Klimov" <grandmaster@al2klimov.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Chris Zankel <chris@zankel.net>
Cc: Corentin Labbe <clabbe@baylibre.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Gregory Clement <gregory.clement@bootlin.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hillf Danton <hdanton@sina.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: James Troup <james.troup@canonical.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kairui Song <kasong@redhat.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: openrisc@lists.librecores.org
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Pavel Machek (CIP)" <pavel@denx.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: sparclinux@vger.kernel.org
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Theodore Dubois <tblodt@icloud.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: William Cohen <wcohen@redhat.com>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

configs: get rid of obsolete CONFIG_ENABLE_WARN_DEPRECATED

This Kconfig option was removed during v4.19 development in commit
771c035372a0 ("deprecate the '__deprecated' attribute warnings entirely

configs: get rid of obsolete CONFIG_ENABLE_WARN_DEPRECATED

This Kconfig option was removed during v4.19 development in commit
771c035372a0 ("deprecate the '__deprecated' attribute warnings entirely
and for good") so there's no point to keep it in defconfigs any longer.

FWIW defconfigs were patched with:
--------------------------->8----------------------
find . -name *_defconfig -exec sed -i '/CONFIG_ENABLE_WARN_DEPRECATED/d' {} \;
--------------------------->8----------------------

Link: http://lkml.kernel.org/r/20190128152434.41969-1-abrodkin@synopsys.com
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

sh: defconfig: cleanup from old Kconfig options

Remove old, dead Kconfig options (in order appearing in this commit):
- EXPERIMENTAL is gone since v3.9;
- INET_LRO: commit 7bbf3cae65b6 ("ipv4: Rem

sh: defconfig: cleanup from old Kconfig options

Remove old, dead Kconfig options (in order appearing in this commit):
- EXPERIMENTAL is gone since v3.9;
- INET_LRO: commit 7bbf3cae65b6 ("ipv4: Remove inet_lro library");
- MTD_CONCAT: commit f53fdebcc3e1 ("mtd: drop MTD_CONCAT from Kconfig
entirely");
- MTD_PARTITIONS: commit 6a8a98b22b10 ("mtd: kill
CONFIG_MTD_PARTITIONS");
- MTD_CHAR: commit 660685d9d1b4 ("mtd: merge mtdchar module with
mtdcore");
- NETDEV_1000 and NETDEV_10000: commit f860b0522f65 ("drivers/net:
Kconfig and Makefile cleanup"); NET_ETHERNET should be replaced with
just ETHERNET but that is separate change;
- HID_SUPPORT: commit 1f41a6a99476 ("HID: Fix the generic Kconfig
options");
- RCU_CPU_STALL_DETECTOR: commit a00e0d714fbd ("rcu: Remove conditional
compilation for RCU CPU stall warnings");
- SYSCTL_SYSCALL_CHECK: commit 7c60c48f58a7 ("sysctl: Improve the
sysctl sanity checks");
- VIDEO_OUTPUT_CONTROL: commit f167a64e9d67 ("video / output: Drop
display output class support");
- MISC_DEVICES: commit 7c5763b8453a ("drivers: misc: Remove
MISC_DEVICES config option");
- AUTOFS_FS: commit 561c5cf9236a ("staging: Remove autofs3");
- IP_NF_QUEUE: commit 3dd6664fac7e ("netfilter: remove unused "config
IP_NF_QUEUE"");
- USB_DEVICE_CLASS: commit 007bab91324e ("USB: remove
CONFIG_USB_DEVICE_CLASS");
- USB_LIBUSUAL: commit f61870ee6f8c ("usb: remove libusual");
- DISPLAY_SUPPORT: commit 5a6b5e02d673 ("fbdev: remove display
subsystem");
- IP_NF_TARGET_ULOG: commit d4da843e6fad ("netfilter: kill remnants of
ulog targets");
- IP6_NF_QUEUE: commit d16cf20e2f2f ("netfilter: remove ip_queue
support");
- IP6_NF_TARGET_LOG: commit 6939c33a757b ("netfilter: merge ipt_LOG and
ip6_LOG into xt_LOG");

Link: http://lkml.kernel.org/r/1500526846-4072-1-git-send-email-krzk@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

defconfig reduction

Use the defconfig files generated by "make savedefconfig" for
remaining defconfig files.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: defconfig updates.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs for PCI changes.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: Add a simple edosk7705_defconfig for build testing.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

configs: get rid of obsolete CONFIG_ENABLE_WARN_DEPRECATED

This Kconfig option was removed during v4.19 development in commit
771c035372a0 ("deprecate the '__deprecated' attribute warnin

configs: get rid of obsolete CONFIG_ENABLE_WARN_DEPRECATED

This Kconfig option was removed during v4.19 development in commit
771c035372a0 ("deprecate the '__deprecated' attribute warnings entirely
and for good") so there's no point to keep it in defconfigs any longer.

FWIW defconfigs were patched with:
--------------------------->8----------------------
find . -name *_defconfig -exec sed -i '/CONFIG_ENABLE_WARN_DEPRECATED/d' {} \;
--------------------------->8----------------------

Link: http://lkml.kernel.org/r/20190128152434.41969-1-abrodkin@synopsys.com
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

sh: defconfig: cleanup from old Kconfig options

Remove old, dead Kconfig options (in order appearing in this commit):
- EXPERIMENTAL is gone since v3.9;
- INET_LRO: commit 7bbf3cae

sh: defconfig: cleanup from old Kconfig options

Remove old, dead Kconfig options (in order appearing in this commit):
- EXPERIMENTAL is gone since v3.9;
- INET_LRO: commit 7bbf3cae65b6 ("ipv4: Remove inet_lro library");
- MTD_CONCAT: commit f53fdebcc3e1 ("mtd: drop MTD_CONCAT from Kconfig
entirely");
- MTD_PARTITIONS: commit 6a8a98b22b10 ("mtd: kill
CONFIG_MTD_PARTITIONS");
- MTD_CHAR: commit 660685d9d1b4 ("mtd: merge mtdchar module with
mtdcore");
- NETDEV_1000 and NETDEV_10000: commit f860b0522f65 ("drivers/net:
Kconfig and Makefile cleanup"); NET_ETHERNET should be replaced with
just ETHERNET but that is separate change;
- HID_SUPPORT: commit 1f41a6a99476 ("HID: Fix the generic Kconfig
options");
- RCU_CPU_STALL_DETECTOR: commit a00e0d714fbd ("rcu: Remove conditional
compilation for RCU CPU stall warnings");
- SYSCTL_SYSCALL_CHECK: commit 7c60c48f58a7 ("sysctl: Improve the
sysctl sanity checks");
- VIDEO_OUTPUT_CONTROL: commit f167a64e9d67 ("video / output: Drop
display output class support");
- MISC_DEVICES: commit 7c5763b8453a ("drivers: misc: Remove
MISC_DEVICES config option");
- AUTOFS_FS: commit 561c5cf9236a ("staging: Remove autofs3");
- IP_NF_QUEUE: commit 3dd6664fac7e ("netfilter: remove unused "config
IP_NF_QUEUE"");
- USB_DEVICE_CLASS: commit 007bab91324e ("USB: remove
CONFIG_USB_DEVICE_CLASS");
- USB_LIBUSUAL: commit f61870ee6f8c ("usb: remove libusual");
- DISPLAY_SUPPORT: commit 5a6b5e02d673 ("fbdev: remove display
subsystem");
- IP_NF_TARGET_ULOG: commit d4da843e6fad ("netfilter: kill remnants of
ulog targets");
- IP6_NF_QUEUE: commit d16cf20e2f2f ("netfilter: remove ip_queue
support");
- IP6_NF_TARGET_LOG: commit 6939c33a757b ("netfilter: merge ipt_LOG and
ip6_LOG into xt_LOG");

Link: http://lkml.kernel.org/r/1500526846-4072-1-git-send-email-krzk@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

defconfig reduction

Use the defconfig files generated by "make savedefconfig" for
remaining defconfig files.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: defconfig updates.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs for PCI changes.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: update defconfigs.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

sh: Add a simple edosk7705_defconfig for build testing.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>