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Subject[ 61/70] m68k: Make sys_atomic_cmpxchg_32 work on classic m68k
3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Andreas Schwab <schwab@linux-m68k.org>

commit 9e2760d18b3cf179534bbc27692c84879c61b97c upstream.

User space access must always go through uaccess accessors, since on
classic m68k user space and kernel space are completely separate.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Tested-by: Thorsten Glaser <tg@debian.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/m68k/kernel/sys_m68k.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 8623f8d..9a5932e 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -479,9 +479,13 @@ sys_atomic_cmpxchg_32(unsigned long newval, int oldval, int d3, int d4, int d5,
goto bad_access;
}

- mem_value = *mem;
+ /*
+ * No need to check for EFAULT; we know that the page is
+ * present and writable.
+ */
+ __get_user(mem_value, mem);
if (mem_value == oldval)
- *mem = newval;
+ __put_user(newval, mem);

pte_unmap_unlock(pte, ptl);
up_read(&mm->mmap_sem);



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