[PATCH] probe_kernel_address() needs to do set_fs()
probe_kernel_address() purports to be generic, only it forgot to select
KERNEL_DS, so it presently won't work right on all architectures.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 67918c2..76c3fe3 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -65,14 +65,22 @@
* do_page_fault() doesn't attempt to take mmap_sem. This makes
* probe_kernel_address() suitable for use within regions where the caller
* already holds mmap_sem, or other locks which nest inside mmap_sem.
+ * This must be a macro because __get_user() needs to know the types of the
+ * args.
+ *
+ * We don't include enough header files to be able to do the set_fs(). We
+ * require that the probe_kernel_address() caller will do that.
*/
#define probe_kernel_address(addr, retval) \
({ \
long ret; \
+ mm_segment_t old_fs = get_fs(); \
\
+ set_fs(KERNEL_DS); \
pagefault_disable(); \
ret = __get_user(retval, addr); \
pagefault_enable(); \
+ set_fs(old_fs); \
ret; \
})