binfmt_flat: update libraries' data segment pointer with userspace accessors

This is needed on systems with a MMU.  This also gets rid of the
strangest C code I've seen lateli i.e. an integer indexed with a
pointer value within square brackets. That really looked backwards.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Greg Ungerer <gerg@linux-m68k.org>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>

1 files changed, 13 insertions, 6 deletions

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index eb747a266537..83e507137112 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -894,12 +894,19 @@ static int load_flat_binary(struct linux_binprm *bprm)
                 return res;
 
         /* Update data segment pointers for all libraries */
-        for (i = 0; i < MAX_SHARED_LIBS; i++)
-                if (libinfo.lib_list[i].loaded)
-                        for (j = 0; j < MAX_SHARED_LIBS; j++)
-                                (-(j+1))[(unsigned long *)(libinfo.lib_list[i].start_data)] =
-                                        (libinfo.lib_list[j].loaded) ?
-                                                libinfo.lib_list[j].start_data : UNLOADED_LIB;
+        for (i = 0; i < MAX_SHARED_LIBS; i++) {
+                if (!libinfo.lib_list[i].loaded)
+                        continue;
+                for (j = 0; j < MAX_SHARED_LIBS; j++) {
+                        unsigned long val = libinfo.lib_list[j].loaded ?
+                                libinfo.lib_list[j].start_data : UNLOADED_LIB;
+                        unsigned long __user *p = (unsigned long __user *)
+                                libinfo.lib_list[i].start_data;
+                        p -= j + 1;
+                        if (put_user(val, p))
+                                return -EFAULT;
+                }
+        }
 
         install_exec_creds(bprm);