From bbcd53c960713507ae764bf81970651b5577b95a Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 6 May 2021 18:05:55 -0700 Subject: 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 Looks like it's essentially unused and has been replaced by better suited interfaces for individual tasks (/proc/kcore, KDB/KGDB).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 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 --- arch/hexagon/configs/comet_defconfig | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/hexagon') diff --git a/arch/hexagon/configs/comet_defconfig b/arch/hexagon/configs/comet_defconfig index f19ae2ab0aaa..c5a214716a38 100644 --- a/arch/hexagon/configs/comet_defconfig +++ b/arch/hexagon/configs/comet_defconfig @@ -34,7 +34,6 @@ CONFIG_NET_ETHERNET=y # CONFIG_SERIO is not set # CONFIG_CONSOLE_TRANSLATIONS is not set CONFIG_LEGACY_PTY_COUNT=64 -# CONFIG_DEVKMEM is not set # CONFIG_HW_RANDOM is not set CONFIG_SPI=y CONFIG_SPI_DEBUG=y -- cgit v1.2.3 From f2e762bab9f5ec74cc9860fc24f01b7f58c98659 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 6 May 2021 18:06:01 -0700 Subject: mm: remove xlate_dev_kmem_ptr() Since /dev/kmem has been removed, let's remove the xlate_dev_kmem_ptr() leftovers. Link: https://lkml.kernel.org/r/20210324102351.6932-3-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Geert Uytterhoeven Acked-by: Michal Hocko Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Matt Turner Cc: Russell King Cc: Brian Cain Cc: Geert Uytterhoeven Cc: Thomas Bogendoerfer Cc: "James E.J. Bottomley" Cc: Helge Deller Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Yoshinori Sato Cc: Rich Felker Cc: "David S. Miller" Cc: Arnd Bergmann Cc: David Hildenbrand Cc: Krzysztof Kozlowski Cc: Mikulas Patocka Cc: Luc Van Oostenryck Cc: Mike Rapoport Cc: Palmer Dabbelt Cc: Luis Chamberlain Cc: Greentime Hu Cc: Sebastian Andrzej Siewior Cc: Randy Dunlap Cc: Jiaxun Yang Cc: "Peter Zijlstra (Intel)" Cc: Christophe Leroy Cc: Gerald Schaefer Cc: Niklas Schnelle Cc: Pierre Morel Cc: Ingo Molnar Cc: Kuninori Morimoto Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/alpha/include/asm/io.h | 5 ----- arch/arm/include/asm/io.h | 5 ----- arch/hexagon/include/asm/io.h | 1 - arch/ia64/include/asm/io.h | 1 - arch/ia64/include/asm/uaccess.h | 18 ------------------ arch/m68k/include/asm/io_mm.h | 5 ----- arch/mips/include/asm/io.h | 5 ----- arch/parisc/include/asm/io.h | 5 ----- arch/powerpc/include/asm/io.h | 5 ----- arch/s390/include/asm/io.h | 5 ----- arch/sh/include/asm/io.h | 5 ----- arch/sparc/include/asm/io_64.h | 5 ----- include/asm-generic/io.h | 11 ----------- 13 files changed, 76 deletions(-) (limited to 'arch/hexagon') diff --git a/arch/alpha/include/asm/io.h b/arch/alpha/include/asm/io.h index 1f6a909d1fa5..0fab5ac90775 100644 --- a/arch/alpha/include/asm/io.h +++ b/arch/alpha/include/asm/io.h @@ -602,11 +602,6 @@ extern void outsl (unsigned long port, const void *src, unsigned long count); */ #define xlate_dev_mem_ptr(p) __va(p) -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - #endif /* __KERNEL__ */ #endif /* __ALPHA_IO_H */ diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h index fc748122f1e0..f74944c6fe8d 100644 --- a/arch/arm/include/asm/io.h +++ b/arch/arm/include/asm/io.h @@ -430,11 +430,6 @@ extern void pci_iounmap(struct pci_dev *dev, void __iomem *addr); */ #define xlate_dev_mem_ptr(p) __va(p) -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - #include #ifdef CONFIG_MMU diff --git a/arch/hexagon/include/asm/io.h b/arch/hexagon/include/asm/io.h index bda2a9c2df78..c33241425a5c 100644 --- a/arch/hexagon/include/asm/io.h +++ b/arch/hexagon/include/asm/io.h @@ -64,7 +64,6 @@ static inline void *phys_to_virt(unsigned long address) * convert a physical pointer to a virtual kernel pointer for * /dev/mem access. */ -#define xlate_dev_kmem_ptr(p) __va(p) #define xlate_dev_mem_ptr(p) __va(p) /* diff --git a/arch/ia64/include/asm/io.h b/arch/ia64/include/asm/io.h index 3d666a11a2de..6d93b923b379 100644 --- a/arch/ia64/include/asm/io.h +++ b/arch/ia64/include/asm/io.h @@ -277,7 +277,6 @@ extern void memset_io(volatile void __iomem *s, int c, long n); #define memcpy_fromio memcpy_fromio #define memcpy_toio memcpy_toio #define memset_io memset_io -#define xlate_dev_kmem_ptr xlate_dev_kmem_ptr #define xlate_dev_mem_ptr xlate_dev_mem_ptr #include #undef PCI_IOBASE diff --git a/arch/ia64/include/asm/uaccess.h b/arch/ia64/include/asm/uaccess.h index 179243c3dfc7..e19d2dcc0ced 100644 --- a/arch/ia64/include/asm/uaccess.h +++ b/arch/ia64/include/asm/uaccess.h @@ -272,22 +272,4 @@ xlate_dev_mem_ptr(phys_addr_t p) return ptr; } -/* - * Convert a virtual cached kernel memory pointer to an uncached pointer - */ -static __inline__ void * -xlate_dev_kmem_ptr(void *p) -{ - struct page *page; - void *ptr; - - page = virt_to_page((unsigned long)p); - if (PageUncached(page)) - ptr = (void *)__pa(p) + __IA64_UNCACHED_OFFSET; - else - ptr = p; - - return ptr; -} - #endif /* _ASM_IA64_UACCESS_H */ diff --git a/arch/m68k/include/asm/io_mm.h b/arch/m68k/include/asm/io_mm.h index 819f611dccf2..d41fa488453b 100644 --- a/arch/m68k/include/asm/io_mm.h +++ b/arch/m68k/include/asm/io_mm.h @@ -397,11 +397,6 @@ static inline void isa_delay(void) */ #define xlate_dev_mem_ptr(p) __va(p) -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - #define readb_relaxed(addr) readb(addr) #define readw_relaxed(addr) readw(addr) #define readl_relaxed(addr) readl(addr) diff --git a/arch/mips/include/asm/io.h b/arch/mips/include/asm/io.h index 2c138450ad3b..6f5c86d2bab4 100644 --- a/arch/mips/include/asm/io.h +++ b/arch/mips/include/asm/io.h @@ -564,11 +564,6 @@ extern void (*_dma_cache_inv)(unsigned long start, unsigned long size); */ #define xlate_dev_mem_ptr(p) __va(p) -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - void __ioread64_copy(void *to, const void __iomem *from, size_t count); #endif /* _ASM_IO_H */ diff --git a/arch/parisc/include/asm/io.h b/arch/parisc/include/asm/io.h index 8a11b8cf4719..0b5259102319 100644 --- a/arch/parisc/include/asm/io.h +++ b/arch/parisc/include/asm/io.h @@ -316,11 +316,6 @@ extern void iowrite64be(u64 val, void __iomem *addr); */ #define xlate_dev_mem_ptr(p) __va(p) -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - extern int devmem_is_allowed(unsigned long pfn); #endif diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h index 273edd208ec5..f130783c8301 100644 --- a/arch/powerpc/include/asm/io.h +++ b/arch/powerpc/include/asm/io.h @@ -662,11 +662,6 @@ static inline void name at \ */ #define xlate_dev_mem_ptr(p) __va(p) -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - /* * We don't do relaxed operations yet, at least not with this semantic */ diff --git a/arch/s390/include/asm/io.h b/arch/s390/include/asm/io.h index 28664ee0abc1..e3882b012bfa 100644 --- a/arch/s390/include/asm/io.h +++ b/arch/s390/include/asm/io.h @@ -20,11 +20,6 @@ void *xlate_dev_mem_ptr(phys_addr_t phys); #define unxlate_dev_mem_ptr unxlate_dev_mem_ptr void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr); -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - #define IO_SPACE_LIMIT 0 void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long prot); diff --git a/arch/sh/include/asm/io.h b/arch/sh/include/asm/io.h index 6d5c6463bc07..cf9a3ec32406 100644 --- a/arch/sh/include/asm/io.h +++ b/arch/sh/include/asm/io.h @@ -283,11 +283,6 @@ static inline void __iomem *ioremap_prot(phys_addr_t offset, unsigned long size, */ #define xlate_dev_mem_ptr(p) __va(p) -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - #define ARCH_HAS_VALID_PHYS_ADDR_RANGE int valid_phys_addr_range(phys_addr_t addr, size_t size); int valid_mmap_phys_addr_range(unsigned long pfn, size_t size); diff --git a/arch/sparc/include/asm/io_64.h b/arch/sparc/include/asm/io_64.h index 9fbfc9574432..5ffa820dcd4d 100644 --- a/arch/sparc/include/asm/io_64.h +++ b/arch/sparc/include/asm/io_64.h @@ -454,11 +454,6 @@ void sbus_set_sbus64(struct device *, int); */ #define xlate_dev_mem_ptr(p) __va(p) -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#define xlate_dev_kmem_ptr(p) p - #endif #endif /* !(__SPARC64_IO_H) */ diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h index 76d456c516a1..e93375c710b9 100644 --- a/include/asm-generic/io.h +++ b/include/asm-generic/io.h @@ -1064,17 +1064,6 @@ static inline void pci_iounmap(struct pci_dev *dev, void __iomem *p) #endif #endif /* CONFIG_GENERIC_IOMAP */ -/* - * Convert a virtual cached pointer to an uncached pointer - */ -#ifndef xlate_dev_kmem_ptr -#define xlate_dev_kmem_ptr xlate_dev_kmem_ptr -static inline void *xlate_dev_kmem_ptr(void *addr) -{ - return addr; -} -#endif - #ifndef xlate_dev_mem_ptr #define xlate_dev_mem_ptr xlate_dev_mem_ptr static inline void *xlate_dev_mem_ptr(phys_addr_t addr) -- cgit v1.2.3