From 12700c17fc286149324f92d6d380bc48e43f253d Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 15 Feb 2022 17:55:04 +0100 Subject: uaccess: generalize access_ok() There are many different ways that access_ok() is defined across architectures, but in the end, they all just compare against the user_addr_max() value or they accept anything. Provide one definition that works for most architectures, checking against TASK_SIZE_MAX for user processes or skipping the check inside of uaccess_kernel() sections. For architectures without CONFIG_SET_FS(), this should be the fastest check, as it comes down to a single comparison of a pointer against a compile-time constant, while the architecture specific versions tend to do something more complex for historic reasons or get something wrong. Type checking for __user annotations is handled inconsistently across architectures, but this is easily simplified as well by using an inline function that takes a 'const void __user *' argument. A handful of callers need an extra __user annotation for this. Some architectures had trick to use 33-bit or 65-bit arithmetic on the addresses to calculate the overflow, however this simpler version uses fewer registers, which means it can produce better object code in the end despite needing a second (statically predicted) branch. Reviewed-by: Christoph Hellwig Acked-by: Mark Rutland [arm64, asm-generic] Acked-by: Geert Uytterhoeven Acked-by: Stafford Horne Acked-by: Dinh Nguyen Signed-off-by: Arnd Bergmann --- include/asm-generic/access_ok.h | 60 +++++++++++++++++++++++++++++++++++++++++ include/asm-generic/uaccess.h | 21 +-------------- include/linux/uaccess.h | 7 ----- 3 files changed, 61 insertions(+), 27 deletions(-) create mode 100644 include/asm-generic/access_ok.h (limited to 'include') diff --git a/include/asm-generic/access_ok.h b/include/asm-generic/access_ok.h new file mode 100644 index 000000000000..d38cc5dad65b --- /dev/null +++ b/include/asm-generic/access_ok.h @@ -0,0 +1,60 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_GENERIC_ACCESS_OK_H__ +#define __ASM_GENERIC_ACCESS_OK_H__ + +/* + * Checking whether a pointer is valid for user space access. + * These definitions work on most architectures, but overrides can + * be used where necessary. + */ + +/* + * architectures with compat tasks have a variable TASK_SIZE and should + * override this to a constant. + */ +#ifndef TASK_SIZE_MAX +#define TASK_SIZE_MAX TASK_SIZE +#endif + +#ifndef uaccess_kernel +#ifdef CONFIG_SET_FS +#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg) +#else +#define uaccess_kernel() (0) +#endif +#endif + +#ifndef user_addr_max +#define user_addr_max() (uaccess_kernel() ? ~0UL : TASK_SIZE_MAX) +#endif + +#ifndef __access_ok +/* + * 'size' is a compile-time constant for most callers, so optimize for + * this case to turn the check into a single comparison against a constant + * limit and catch all possible overflows. + * On architectures with separate user address space (m68k, s390, parisc, + * sparc64) or those without an MMU, this should always return true. + * + * This version was originally contributed by Jonas Bonn for the + * OpenRISC architecture, and was found to be the most efficient + * for constant 'size' and 'limit' values. + */ +static inline int __access_ok(const void __user *ptr, unsigned long size) +{ + unsigned long limit = user_addr_max(); + unsigned long addr = (unsigned long)ptr; + + if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) || + !IS_ENABLED(CONFIG_MMU)) + return true; + + return (size <= limit) && (addr <= (limit - size)); +} +#endif + +#ifndef access_ok +#define access_ok(addr, size) likely(__access_ok(addr, size)) +#endif + +#endif diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h index 0870fa11a7c5..ebc685dc8d74 100644 --- a/include/asm-generic/uaccess.h +++ b/include/asm-generic/uaccess.h @@ -114,28 +114,9 @@ static inline void set_fs(mm_segment_t fs) } #endif -#ifndef uaccess_kernel -#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg) -#endif - -#ifndef user_addr_max -#define user_addr_max() (uaccess_kernel() ? ~0UL : TASK_SIZE) -#endif - #endif /* CONFIG_SET_FS */ -#define access_ok(addr, size) __access_ok((unsigned long)(addr),(size)) - -/* - * The architecture should really override this if possible, at least - * doing a check on the get_fs() - */ -#ifndef __access_ok -static inline int __access_ok(unsigned long addr, unsigned long size) -{ - return 1; -} -#endif +#include /* * These are the main single-value transfer routines. They automatically diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 67e9bc94dc40..2c31667e62e0 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -33,13 +33,6 @@ typedef struct { /* empty dummy */ } mm_segment_t; -#ifndef TASK_SIZE_MAX -#define TASK_SIZE_MAX TASK_SIZE -#endif - -#define uaccess_kernel() (false) -#define user_addr_max() (TASK_SIZE_MAX) - static inline mm_segment_t force_uaccess_begin(void) { return (mm_segment_t) { }; -- cgit v1.2.3