From 9f0cf4adb6aa0bfccf675c938124e68f7f06349d Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Sat, 26 Sep 2009 14:33:01 +0200 Subject: x86: Use __builtin_object_size() to validate the buffer size for copy_from_user() gcc (4.x) supports the __builtin_object_size() builtin, which reports the size of an object that a pointer point to, when known at compile time. If the buffer size is not known at compile time, a constant -1 is returned. This patch uses this feature to add a sanity check to copy_from_user(); if the target buffer is known to be smaller than the copy size, the copy is aborted and a WARNing is emitted in memory debug mode. These extra checks compile away when the object size is not known, or if both the buffer size and the copy length are constants. Signed-off-by: Arjan van de Ven LKML-Reference: <20090926143301.2c396b94@infradead.org> Signed-off-by: Ingo Molnar diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h index 632fb44..582d6ae 100644 --- a/arch/x86/include/asm/uaccess_32.h +++ b/arch/x86/include/asm/uaccess_32.h @@ -187,9 +187,26 @@ __copy_from_user_inatomic_nocache(void *to, const void __user *from, unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n); -unsigned long __must_check copy_from_user(void *to, +unsigned long __must_check _copy_from_user(void *to, const void __user *from, unsigned long n); + +static inline unsigned long __must_check copy_from_user(void *to, + const void __user *from, + unsigned long n) +{ + int sz = __compiletime_object_size(to); + int ret = -EFAULT; + + if (likely(sz == -1 || sz >= n)) + ret = _copy_from_user(to, from, n); +#ifdef CONFIG_DEBUG_VM + else + WARN(1, "Buffer overflow detected!\n"); +#endif + return ret; +} + long __must_check strncpy_from_user(char *dst, const char __user *src, long count); long __must_check __strncpy_from_user(char *dst, diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index db24b21..ce6fec7 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -21,10 +21,27 @@ copy_user_generic(void *to, const void *from, unsigned len); __must_check unsigned long copy_to_user(void __user *to, const void *from, unsigned len); __must_check unsigned long -copy_from_user(void *to, const void __user *from, unsigned len); +_copy_from_user(void *to, const void __user *from, unsigned len); __must_check unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len); +static inline unsigned long __must_check copy_from_user(void *to, + const void __user *from, + unsigned long n) +{ + int sz = __compiletime_object_size(to); + int ret = -EFAULT; + + if (likely(sz == -1 || sz >= n)) + ret = _copy_from_user(to, from, n); +#ifdef CONFIG_DEBUG_VM + else + WARN(1, "Buffer overflow detected!\n"); +#endif + return ret; +} + + static __always_inline __must_check int __copy_from_user(void *dst, const void __user *src, unsigned size) { diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c index 3909e3b..a0cdd8c 100644 --- a/arch/x86/kernel/x8664_ksyms_64.c +++ b/arch/x86/kernel/x8664_ksyms_64.c @@ -30,7 +30,7 @@ EXPORT_SYMBOL(__put_user_8); EXPORT_SYMBOL(copy_user_generic); EXPORT_SYMBOL(__copy_user_nocache); -EXPORT_SYMBOL(copy_from_user); +EXPORT_SYMBOL(_copy_from_user); EXPORT_SYMBOL(copy_to_user); EXPORT_SYMBOL(__copy_from_user_inatomic); diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S index 6ba0f7b..4be3c41 100644 --- a/arch/x86/lib/copy_user_64.S +++ b/arch/x86/lib/copy_user_64.S @@ -78,7 +78,7 @@ ENTRY(copy_to_user) ENDPROC(copy_to_user) /* Standard copy_from_user with segment limit checking */ -ENTRY(copy_from_user) +ENTRY(_copy_from_user) CFI_STARTPROC GET_THREAD_INFO(%rax) movq %rsi,%rcx @@ -88,7 +88,7 @@ ENTRY(copy_from_user) jae bad_from_user ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string CFI_ENDPROC -ENDPROC(copy_from_user) +ENDPROC(_copy_from_user) ENTRY(copy_user_generic) CFI_STARTPROC diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c index 1f118d4..8498684 100644 --- a/arch/x86/lib/usercopy_32.c +++ b/arch/x86/lib/usercopy_32.c @@ -874,7 +874,7 @@ EXPORT_SYMBOL(copy_to_user); * data to the requested size using zero bytes. */ unsigned long -copy_from_user(void *to, const void __user *from, unsigned long n) +_copy_from_user(void *to, const void __user *from, unsigned long n) { if (access_ok(VERIFY_READ, from, n)) n = __copy_from_user(to, from, n); @@ -882,4 +882,4 @@ copy_from_user(void *to, const void __user *from, unsigned long n) memset(to, 0, n); return n; } -EXPORT_SYMBOL(copy_from_user); +EXPORT_SYMBOL(_copy_from_user); diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h index 450fa59..a3aef5d 100644 --- a/include/linux/compiler-gcc4.h +++ b/include/linux/compiler-gcc4.h @@ -37,3 +37,5 @@ #define __cold __attribute__((__cold__)) #endif + +#define __compiletime_object_size(obj) __builtin_object_size(obj, 0) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 04fb513..8e54108 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -266,6 +266,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) #endif +/* Compile time object size, -1 for unknown */ +#ifndef __compiletime_object_size +# define __compiletime_object_size(obj) -1 +#endif /* * Prevent the compiler from merging or refetching accesses. The compiler * is also forbidden from reordering successive instances of ACCESS_ONCE(), -- cgit v0.10.2