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SubjectRe: [PATCH] use size_t for the broken ioctl numbers
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On Monday 08 September 2003 01:21, Linus Torvalds wrote:

> In fact, what you'd want to do is not just verify that it compiles, but
> also verify that the object code matches.

I have checked now that the object code for arch/s390/kernel/compat_ioctl.o
remains identical and that the whole kernel compiles for s390 and i386,
after fixing the broken ioctl numbers.

> Because there _is_ one case where adding the [1] will still compile, but
> generate wrong code: if the "size" argument to the _IOx() was not a type,
> but a real actual array.

Yes, there had to be a catch. The new version below catches that error
too, making that a link time failure and also checks that the size
field does not overflow.

Arnd <><

--- 1.1/include/asm-i386/ioctl.h Tue Feb 5 18:39:44 2002
+++ edited/include/asm-i386/ioctl.h Mon Sep 8 13:21:28 2003
@@ -52,11 +52,21 @@
((nr) << _IOC_NRSHIFT) | \
((size) << _IOC_SIZESHIFT))

+/* provoke compile error for invalid uses of size argument */
+extern int __invalid_size_argument_for_IOC;
+#define _IOC_TYPECHECK(t) \
+ ((sizeof(t) == sizeof(t[1]) && \
+ sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
+ sizeof(t) : __invalid_size_argument_for_IOC)
+
/* used to create numbers */
#define _IO(type,nr) _IOC(_IOC_NONE,(type),(nr),0)
-#define _IOR(type,nr,size) _IOC(_IOC_READ,(type),(nr),sizeof(size))
-#define _IOW(type,nr,size) _IOC(_IOC_WRITE,(type),(nr),sizeof(size))
-#define _IOWR(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(size))
+#define _IOR(type,nr,size) _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size)))
+#define _IOW(type,nr,size) _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
+#define _IOWR(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
+#define _IOR_BAD(type,nr,size) _IOC(_IOC_READ,(type),(nr),sizeof(size))
+#define _IOW_BAD(type,nr,size) _IOC(_IOC_WRITE,(type),(nr),sizeof(size))
+#define _IOWR_BAD(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(size))

/* used to decode ioctl numbers.. */
#define _IOC_DIR(nr) (((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK)
-
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