compat: Make compat_alloc_user_space() incorporate the access_ok()

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 <hawkes@sota.gen.nz>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Tony Luck <tony.luck@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: James Bottomley <jejb@parisc-linux.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 5 insertions, 3 deletions

diff --git a/include/asm-mips/compat.h b/include/asm-mips/compat.h
index 6c5b40905dd6..8df5ceeeb63d 100644
--- a/include/asm-mips/compat.h
+++ b/include/asm-mips/compat.h
@@ -145,7 +145,7 @@ static inline compat_uptr_t ptr_to_compat(void __user *uptr)
 	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;
diff --git a/include/asm-parisc/compat.h b/include/asm-parisc/compat.h
index 7f32611a7a5e..7c77fa93ab33 100644
--- a/include/asm-parisc/compat.h
+++ b/include/asm-parisc/compat.h
@@ -146,7 +146,7 @@ static inline compat_uptr_t ptr_to_compat(void __user *uptr)
 	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;
 	return (void __user *)regs->gr[30];
diff --git a/include/asm-x86/compat.h b/include/asm-x86/compat.h
index 1793ac317a30..8b1b00e8784c 100644
--- a/include/asm-x86/compat.h
+++ b/include/asm-x86/compat.h
@@ -204,7 +204,7 @@ static inline compat_uptr_t ptr_to_compat(void __user *uptr)
 	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;
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 275b9bd8c4df..8cb2fcf21700 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -291,5 +291,7 @@ asmlinkage long compat_sys_newfstatat(unsigned int dfd, char __user * filename,
 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 */