[PATCH 04/14] x86: use more conventional access_ok() definition
From: Arnd Bergmann <arnd@kernel.org>
Date: 2022-02-14 16:37:28
Also in:
linux-alpha, linux-api, linux-arch, linux-arm-kernel, linux-m68k, linux-mips, linux-mm, linux-riscv, linux-s390, linux-sh, linux-um, lkml, sparclinux
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Arnd Bergmann <arnd@arndb.de> The way that access_ok() is defined on x86 is slightly different from most other architectures, and a bit more complex. The generic version tends to result in the best output on all architectures, as it results in single comparison against a constant limit for calls with a known size. There are a few callers of __range_not_ok(), all of which use TASK_SIZE as the limit rather than TASK_SIZE_MAX, but I could not see any reason for picking this. Changing these to call __access_ok() instead uses the default limit, but keeps the behavior otherwise. x86 is the only architecture with a WARN_ON_IN_IRQ() checking access_ok(), but it's probably best to leave that in place. Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- arch/x86/include/asm/uaccess.h | 38 +++++++++++----------------------- 1 file changed, 12 insertions(+), 26 deletions(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index ac96f9b2d64b..6956a63291b6 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h@@ -16,30 +16,13 @@ * Test whether a block of memory is a valid user space address. * Returns 0 if the range is valid, nonzero otherwise. */ -static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit) +static inline bool __access_ok(void __user *ptr, unsigned long size) { - /* - * If we have used "sizeof()" for the size, - * we know it won't overflow the limit (but - * it might overflow the 'addr', so it's - * important to subtract the size from the - * limit, not add it to the address). - */ - if (__builtin_constant_p(size)) - return unlikely(addr > limit - size); - - /* Arbitrary sizes? Be careful about overflow */ - addr += size; - if (unlikely(addr < size)) - return true; - return unlikely(addr > limit); -} + unsigned long limit = TASK_SIZE_MAX; + unsigned long addr = ptr; -#define __range_not_ok(addr, size, limit) \ -({ \ - __chk_user_ptr(addr); \ - __chk_range_not_ok((unsigned long __force)(addr), size, limit); \ -}) + return (size <= limit) && (addr <= (limit - size)); +} #ifdef CONFIG_DEBUG_ATOMIC_SLEEP static inline bool pagefault_disabled(void);
@@ -66,12 +49,15 @@ static inline bool pagefault_disabled(void); * Return: true (nonzero) if the memory block may be valid, false (zero) * if it is definitely invalid. */ -#define access_ok(addr, size) \ -({ \ - WARN_ON_IN_IRQ(); \ - likely(!__range_not_ok(addr, size, TASK_SIZE_MAX)); \ +#define access_ok(addr, size) \ +({ \ + WARN_ON_IN_IRQ(); \ + likely(__access_ok(addr, size));\ }) +#define __range_not_ok(addr, size, limit) (!__access_ok(addr, size)) +#define __chk_range_not_ok(addr, size, limit) (!__access_ok((void __user *)addr, size)) + extern int __get_user_1(void); extern int __get_user_2(void); extern int __get_user_4(void);
--
2.29.2