From: H. Peter Anvin commit c41d68a513c71e35a14f66d71782d27a79a81ea6 upstream. compat_alloc_user_space() expects the caller to independently call access_ok() to verify the returned area. A missing call could introduce problems on some architectures. This patch incorporates the access_ok() check into compat_alloc_user_space() and also adds a sanity check on the length. The existing compat_alloc_user_space() implementations are renamed arch_compat_alloc_user_space() and are used as part of the implementation of the new global function. This patch assumes NULL will cause __get_user()/__put_user() to either fail or access userspace on all architectures. This should be followed by checking the return value of compat_access_user_space() for NULL in the callers, at which time the access_ok() in the callers can also be removed. Reported-by: Ben Hawkes Signed-off-by: H. Peter Anvin Acked-by: Benjamin Herrenschmidt Acked-by: Chris Metcalf Acked-by: David S. Miller Acked-by: Ingo Molnar Acked-by: Thomas Gleixner Acked-by: Tony Luck Cc: Andrew Morton Cc: Arnd Bergmann Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Heiko Carstens Cc: Helge Deller Cc: James Bottomley Cc: Kyle McMartin Cc: Martin Schwidefsky Cc: Paul Mackerras Cc: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/ia64/include/asm/compat.h | 2 +- arch/mips/include/asm/compat.h | 2 +- arch/parisc/include/asm/compat.h | 2 +- arch/powerpc/include/asm/compat.h | 2 +- arch/s390/include/asm/compat.h | 2 +- arch/sparc/include/asm/compat.h | 2 +- arch/x86/include/asm/compat.h | 2 +- include/linux/compat.h | 2 ++ kernel/compat.c | 22 ++++++++++++++++++++++ 9 files changed, 31 insertions(+), 7 deletions(-) --- a/arch/ia64/include/asm/compat.h +++ b/arch/ia64/include/asm/compat.h @@ -198,7 +198,7 @@ ptr_to_compat(void __user *uptr) } static __inline__ void __user * -compat_alloc_user_space (long len) +arch_compat_alloc_user_space (long len) { struct pt_regs *regs = task_pt_regs(current); return (void __user *) (((regs->r12 & 0xffffffff) & -16) - len); --- a/arch/mips/include/asm/compat.h +++ b/arch/mips/include/asm/compat.h @@ -144,7 +144,7 @@ static inline compat_uptr_t ptr_to_compa return (u32)(unsigned long)uptr; } -static inline void __user *compat_alloc_user_space(long len) +static inline void __user *arch_compat_alloc_user_space(long len) { struct pt_regs *regs = (struct pt_regs *) ((unsigned long) current_thread_info() + THREAD_SIZE - 32) - 1; --- a/arch/parisc/include/asm/compat.h +++ b/arch/parisc/include/asm/compat.h @@ -146,7 +146,7 @@ static inline compat_uptr_t ptr_to_compa return (u32)(unsigned long)uptr; } -static __inline__ void __user *compat_alloc_user_space(long len) +static __inline__ void __user *arch_compat_alloc_user_space(long len) { struct pt_regs *regs = ¤t->thread.regs; return (void __user *)regs->gr[30]; --- a/arch/powerpc/include/asm/compat.h +++ b/arch/powerpc/include/asm/compat.h @@ -133,7 +133,7 @@ static inline compat_uptr_t ptr_to_compa return (u32)(unsigned long)uptr; } -static inline void __user *compat_alloc_user_space(long len) +static inline void __user *arch_compat_alloc_user_space(long len) { struct pt_regs *regs = current->thread.regs; unsigned long usp = regs->gpr[1]; --- a/arch/s390/include/asm/compat.h +++ b/arch/s390/include/asm/compat.h @@ -180,7 +180,7 @@ static inline int is_compat_task(void) #endif -static inline void __user *compat_alloc_user_space(long len) +static inline void __user *arch_compat_alloc_user_space(long len) { unsigned long stack; --- a/arch/sparc/include/asm/compat.h +++ b/arch/sparc/include/asm/compat.h @@ -166,7 +166,7 @@ static inline compat_uptr_t ptr_to_compa return (u32)(unsigned long)uptr; } -static inline void __user *compat_alloc_user_space(long len) +static inline void __user *arch_compat_alloc_user_space(long len) { struct pt_regs *regs = current_thread_info()->kregs; unsigned long usp = regs->u_regs[UREG_I6]; --- a/arch/x86/include/asm/compat.h +++ b/arch/x86/include/asm/compat.h @@ -204,7 +204,7 @@ static inline compat_uptr_t ptr_to_compa return (u32)(unsigned long)uptr; } -static inline void __user *compat_alloc_user_space(long len) +static inline void __user *arch_compat_alloc_user_space(long len) { struct pt_regs *regs = task_pt_regs(current); return (void __user *)regs->sp - len; --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -309,5 +309,7 @@ asmlinkage long compat_sys_newfstatat(un asmlinkage long compat_sys_openat(unsigned int dfd, const char __user *filename, int flags, int mode); +extern void __user *compat_alloc_user_space(unsigned long len); + #endif /* CONFIG_COMPAT */ #endif /* _LINUX_COMPAT_H */ --- a/kernel/compat.c +++ b/kernel/compat.c @@ -25,6 +25,7 @@ #include #include #include +#include #include @@ -1136,3 +1137,24 @@ compat_sys_sysinfo(struct compat_sysinfo return 0; } + +/* + * Allocate user-space memory for the duration of a single system call, + * in order to marshall parameters inside a compat thunk. + */ +void __user *compat_alloc_user_space(unsigned long len) +{ + void __user *ptr; + + /* If len would occupy more than half of the entire compat space... */ + if (unlikely(len > (((compat_uptr_t)~0) >> 1))) + return NULL; + + ptr = arch_compat_alloc_user_space(len); + + if (unlikely(!access_ok(VERIFY_WRITE, ptr, len))) + return NULL; + + return ptr; +} +EXPORT_SYMBOL_GPL(compat_alloc_user_space); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/