[PATCH] uml: make 64-bit COW files compatible with 32-bit ones

This is the minimal fix to make 64-bit UML binaries create 32-bit
compatible COW files and read them.

I've indeed tested that current code doesn't do this - the code gets
SIGFPE for a division by a value read at the wrong place, where 0 is
found.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[email protected]>
Cc: Jeff Dike <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Paolo 'Blaisorblade' Giarrusso

arch/um/drivers/cow_user.c

@@ -100,7 +100,7 @@ struct cow_header_v3_broken {
 	__u32 alignment;
 	__u32 cow_format;
 	char backing_file[PATH_LEN_V3];
-};
+} __attribute__((packed));
 
 /* COW format definitions - for now, we have only the usual COW bitmap */
 #define COW_BITMAP 0