fs/binfmt_elf.c: fix ->start_code calculation

Only executable segments should be accounted to ->start_code just like
they do to ->end_code (correctly).

Link: http://lkml.kernel.org/r/20191208171410.GB19716@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/binfmt_elf.c

@@ -999,7 +999,7 @@ out_free_interp:
 			}
 		}
 		k = elf_ppnt->p_vaddr;
-		if (k < start_code)
+		if ((elf_ppnt->p_flags & PF_X) && k < start_code)
 			start_code = k;
 		if (start_data < k)
 			start_data = k;