linux-kernel - [ 34/37] s390/compat: fix mmap compat system calls

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Message-Id: <20120817030249.272923423@decadent.org.uk>
Date:	Fri, 17 Aug 2012 04:03:17 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: [ 34/37] s390/compat: fix mmap compat system calls

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Heiko Carstens <heiko.carstens@...ibm.com>

commit e85871218513c54f7dfdb6009043cb638f2fecbe upstream.

The native 31 bit and the compat behaviour for the mmap system calls differ:

In native 31 bit mode the passed in address for the mmap system call will be
unmodified passed to sys_mmap_pgoff().
In compat mode however the passed in address will be modified with
compat_ptr() which masks out the most significant bit.

The result is that in native 31 bit mode each mmap request (with MAP_FIXED)
will fail where the most significat bit is set, while in compat mode it
may succeed.

This odd behaviour was introduced with d3815898 "[S390] mmap: add missing
compat_ptr conversion to both mmap compat syscalls".

To restore a consistent behaviour accross native and compat mode this
patch functionally reverts the above mentioned commit.

Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/s390/kernel/compat_linux.c |    2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index d122508..f606d93 100644
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -620,7 +620,6 @@ asmlinkage unsigned long old32_mmap(struct mmap_arg_struct_emu31 __user *arg)
 		return -EFAULT;
 	if (a.offset & ~PAGE_MASK)
 		return -EINVAL;
-	a.addr = (unsigned long) compat_ptr(a.addr);
 	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
 			      a.offset >> PAGE_SHIFT);
 }
@@ -631,7 +630,6 @@ asmlinkage long sys32_mmap2(struct mmap_arg_struct_emu31 __user *arg)

 	if (copy_from_user(&a, arg, sizeof(a)))
 		return -EFAULT;
-	a.addr = (unsigned long) compat_ptr(a.addr);
 	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, a.offset);
 }

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