kernel/linux.git/drivers/char/mem.c, branch v5.15.7

remove the raw driver

2021-06-04T13:35:03+00:00

The raw driver used to provide direct unbuffered access to block devices before O_DIRECT was invented. It has been obsolete for more than a decade. Acked-by: Greg Kroah-Hartman Acked-by: Arnd Bergmann Link: https://lore.kernel.org/lkml/Pine.LNX.4.64.0703180754060.6605@CPE00045a9c397f-CM001225dbafb6/ Signed-off-by: Christoph Hellwig Link: https://lore.kernel.org/r/20210531072526.97052-1-hch@lst.de Signed-off-by: Greg Kroah-Hartman

drivers/char: remove /dev/kmem for good

2021-05-07T07:26:34+00:00

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 Acked-by: Michal Hocko Acked-by: Kees Cook Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: "Alexander A. Klimov" Cc: Alexander Viro Cc: Alexandre Belloni Cc: Andrew Lunn Cc: Andrey Zhizhikin Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Brian Cain Cc: Christian Borntraeger Cc: Christophe Leroy Cc: Chris Zankel Cc: Corentin Labbe Cc: "David S. Miller" Cc: "Eric W. Biederman" Cc: Geert Uytterhoeven Cc: Gerald Schaefer Cc: Greentime Hu Cc: Gregory Clement Cc: Heiko Carstens Cc: Helge Deller Cc: Hillf Danton Cc: huang ying Cc: Ingo Molnar Cc: Ivan Kokshaysky Cc: "James E.J. Bottomley" Cc: James Troup Cc: Jiaxun Yang Cc: Jonas Bonn Cc: Jonathan Corbet Cc: Kairui Song Cc: Krzysztof Kozlowski Cc: Kuninori Morimoto Cc: Liviu Dudau Cc: Lorenzo Pieralisi Cc: Luc Van Oostenryck Cc: Luis Chamberlain Cc: Matthew Wilcox Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Mike Rapoport Cc: Mikulas Patocka Cc: Minchan Kim Cc: Niklas Schnelle Cc: Oleksiy Avramchenko Cc: openrisc@lists.librecores.org Cc: Palmer Dabbelt Cc: Paul Mackerras Cc: "Pavel Machek (CIP)" Cc: Pavel Machek Cc: "Peter Zijlstra (Intel)" Cc: Pierre Morel Cc: Randy Dunlap Cc: Richard Henderson Cc: Rich Felker Cc: Robert Richter Cc: Rob Herring Cc: Russell King Cc: Sam Ravnborg Cc: Sebastian Andrzej Siewior Cc: Sebastian Hesselbarth Cc: sparclinux@vger.kernel.org Cc: Stafford Horne Cc: Stefan Kristiansson Cc: Steven Rostedt Cc: Sudeep Holla Cc: Theodore Dubois Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Vasily Gorbik Cc: Viresh Kumar Cc: William Cohen Cc: Xiaoming Ni Cc: Yoshinori Sato Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'topic/iomem-mmap-vs-gup-2021-02-22' of git://anongit.freedesktop.org/drm/drm

2021-02-23T01:45:02+00:00

Pull follow_pfn() updates from Daniel Vetter: "Fixes around VM_FPNMAP and follow_pfn: - replace mm/frame_vector.c by get_user_pages in misc/habana and drm/exynos drivers, then move that into media as it's sole user - close race in generic_access_phys - s390 pci ioctl fix of this series landed in 5.11 already - properly revoke iomem mappings (/dev/mem, pci files)" * tag 'topic/iomem-mmap-vs-gup-2021-02-22' of git://anongit.freedesktop.org/drm/drm: PCI: Revoke mappings like devmem PCI: Also set up legacy files only after sysfs init sysfs: Support zapping of binary attr mmaps resource: Move devmem revoke code to resource framework /dev/mem: Only set filp->f_mapping PCI: Obey iomem restrictions for procfs mmap mm: Close race in generic_access_phys media: videobuf2: Move frame_vector into media subsystem mm/frame-vector: Use FOLL_LONGTERM misc/habana: Use FOLL_LONGTERM for userptr misc/habana: Stop using frame_vector helpers drm/exynos: Use FOLL_LONGTERM for g2d cmdlists drm/exynos: Stop using frame_vector helpers

MIPS: mm:remove function __uncached_access()

2021-01-27T20:52:01+00:00

MIPS can now use the default uncached_access like other archs. Signed-off-by: Yanteng Si Acked-by: Greg Kroah-Hartman Signed-off-by: Thomas Bogendoerfer

resource: Move devmem revoke code to resource framework

2021-01-12T13:26:31+00:00

We want all iomem mmaps to consistently revoke ptes when the kernel takes over and CONFIG_IO_STRICT_DEVMEM is enabled. This includes the pci bar mmaps available through procfs and sysfs, which currently do not revoke mappings. To prepare for this, move the code from the /dev/kmem driver to kernel/resource.c. During review Jason spotted that barriers are used somewhat inconsistently. Fix that up while we shuffle this code, since it doesn't have an actual impact at runtime. Otherwise no semantic and behavioural changes intended, just code extraction and adjusting comments and names. Reviewed-by: Greg Kroah-Hartman Signed-off-by: Daniel Vetter Cc: Jason Gunthorpe Cc: Kees Cook Cc: Dan Williams Cc: Andrew Morton Cc: John Hubbard Cc: Jérôme Glisse Cc: Jan Kara Cc: Dan Williams Cc: linux-mm@kvack.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-samsung-soc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Cc: Daniel Vetter Cc: David Hildenbrand Cc: "Rafael J. Wysocki" Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20201127164131.2244124-11-daniel.vetter@ffwll.ch

/dev/mem: Only set filp->f_mapping

2021-01-12T13:26:31+00:00

When we care about pagecache maintenance, we need to make sure that both f_mapping and i_mapping point at the right mapping. But for iomem mappings we only care about the virtual/pte side of things, so f_mapping is enough. Also setting inode->i_mapping was confusing me as a driver maintainer, since in e.g. drivers/gpu we don't do that. Per Dan this seems to be copypasta from places which do care about pagecache consistency, but not needed. Hence remove it for slightly less confusion. Signed-off-by: Daniel Vetter Cc: Jason Gunthorpe Cc: Kees Cook Cc: Dan Williams Cc: Andrew Morton Cc: John Hubbard Cc: Jérôme Glisse Cc: Jan Kara Cc: Dan Williams Cc: linux-mm@kvack.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-samsung-soc@vger.kernel.org Cc: linux-media@vger.kernel.org Reviewed-by: Dan Williams Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20201127164131.2244124-10-daniel.vetter@ffwll.ch

/dev/zero: fixups for ->read

2020-09-07T08:46:35+00:00

Reported the cleared bytes in case of a partial clear_user instead of -EFAULT, and remove a pointless conditional, as cleared must be non-zero by the time we hit the signal_pending check. Reported-by: Rasmus Villemoes Signed-off-by: Christoph Hellwig Link: https://lore.kernel.org/r/20200907082700.2057137-1-hch@lst.de Signed-off-by: Greg Kroah-Hartman

/dev/zero: also implement ->read

2020-09-03T17:50:47+00:00

Christophe reported a major speedup due to avoiding the iov_iter overhead, so just add this trivial function. Note that /dev/zero already implements both an iter and non-iter writes so this just makes it more symmetric. Tested-by: Christophe Leroy Signed-off-by: Christoph Hellwig Link: https://lore.kernel.org/r/20200903155922.1111551-1-hch@lst.de Signed-off-by: Greg Kroah-Hartman

treewide: Use fallthrough pseudo-keyword

2020-08-23T22:36:59+00:00

Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva

/dev/mem: Add missing memory barriers for devmem_inode

2020-07-23T07:47:13+00:00

WRITE_ONCE() isn't the correct way to publish a pointer to a data structure, since it doesn't include a write memory barrier. Therefore other tasks may see that the pointer has been set but not see that the pointed-to memory has finished being initialized yet. Instead a primitive with "release" semantics is needed. Use smp_store_release() for this. The use of READ_ONCE() on the read side is still potentially correct if there's no control dependency, i.e. if all memory being "published" is transitively reachable via the pointer itself. But this pairing is somewhat confusing and error-prone. So just upgrade the read side to smp_load_acquire() so that it clearly pairs with smp_store_release(). Cc: Arnd Bergmann Cc: Ingo Molnar Cc: Kees Cook Cc: Matthew Wilcox Cc: Russell King Cc: Andrew Morton Fixes: 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims the region") Signed-off-by: Eric Biggers Cc: stable Acked-by: Dan Williams Link: https://lore.kernel.org/r/20200716060553.24618-1-ebiggers@kernel.org Signed-off-by: Greg Kroah-Hartman