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Subject[07/11] compat: Make compat_alloc_user_space() incorporate the access_ok()
2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------
From: H. Peter Anvin <hpa@linux.intel.com>

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>

---
arch/ia64/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 +-
include/asm-mips/compat.h | 2 +-
include/asm-parisc/compat.h | 2 +-
include/asm-x86/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/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
@@ -163,7 +163,7 @@ 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)
{
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/include/asm-mips/compat.h
+++ b/include/asm-mips/compat.h
@@ -145,7 +145,7 @@ 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/include/asm-parisc/compat.h
+++ b/include/asm-parisc/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 = &current->thread.regs;
return (void __user *)regs->gr[30];
--- a/include/asm-x86/compat.h
+++ b/include/asm-x86/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
@@ -291,5 +291,7 @@ 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
@@ -23,6 +23,7 @@
#include <linux/timex.h>
#include <linux/migrate.h>
#include <linux/posix-timers.h>
+#include <linux/module.h>

#include <asm/uaccess.h>

@@ -1081,3 +1082,24 @@ 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);



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