mm: fix the MAP_UNINITIALIZED flag

We can't expose UAPI symbols differently based on CONFIG_ symbols, as
userspace won't have them available.  Instead always define the flag,
but only respect it based on the config option.

Link: http://lkml.kernel.org/r/20190703122359.18200-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 7 insertions, 11 deletions

diff --git a/arch/xtensa/include/uapi/asm/mman.h b/arch/xtensa/include/uapi/asm/mman.h
index be726062412b..ebbb48842190 100644
--- a/arch/xtensa/include/uapi/asm/mman.h
+++ b/arch/xtensa/include/uapi/asm/mman.h
@@ -56,12 +56,8 @@
 #define MAP_STACK       0x40000         /* give out an address that is best suited for process/thread stacks */
 #define MAP_HUGETLB     0x80000         /* create a huge page mapping */
 #define MAP_FIXED_NOREPLACE 0x100000    /* MAP_FIXED which doesn't unmap underlying mapping */
-#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED
-# define MAP_UNINITIALIZED 0x4000000    /* For anonymous mmap, memory could be
+#define MAP_UNINITIALIZED 0x4000000     /* For anonymous mmap, memory could be
                                          * uninitialized */
-#else
-# define MAP_UNINITIALIZED 0x0          /* Don't support this flag */
-#endif
 
 /*
  * Flags for msync
diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
index abd238d0f7a4..cb556b430e71 100644
--- a/include/uapi/asm-generic/mman-common.h
+++ b/include/uapi/asm-generic/mman-common.h
@@ -19,15 +19,13 @@
 #define MAP_TYPE        0x0f            /* Mask for type of mapping */
 #define MAP_FIXED       0x10            /* Interpret addr exactly */
 #define MAP_ANONYMOUS   0x20            /* don't use a file */
-#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED
-# define MAP_UNINITIALIZED 0x4000000    /* For anonymous mmap, memory could be uninitialized */
-#else
-# define MAP_UNINITIALIZED 0x0          /* Don't support this flag */
-#endif
 
 /* 0x0100 - 0x80000 flags are defined in asm-generic/mman.h */
 #define MAP_FIXED_NOREPLACE     0x100000        /* MAP_FIXED which doesn't unmap underlying mapping */
 
+#define MAP_UNINITIALIZED 0x4000000     /* For anonymous mmap, memory could be
+                                         * uninitialized */
+
 /*
  * Flags for mlock
  */
diff --git a/mm/nommu.c b/mm/nommu.c
index eb3e2e558da1..fed1b6e9c89b 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1261,7 +1261,9 @@ unsigned long do_mmap(struct file *file,
         add_nommu_region(region);
 
         /* clear anonymous mappings that don't ask for uninitialized data */
-        if (!vma->vm_file && !(flags & MAP_UNINITIALIZED))
+        if (!vma->vm_file &&
+            (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
+             !(flags & MAP_UNINITIALIZED)))
                 memset((void *)region->vm_start, 0,
                        region->vm_end - region->vm_start);