[commit: ghc] master: rts/linker/{SymbolExtras, elf_got}.c: map code as read-only (67c422c)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/67c422ca0e7b94e021430e3dfc9b19f3de21ed16/ghc

>---------------------------------------------------------------

commit 67c422ca0e7b94e021430e3dfc9b19f3de21ed16
Author: Santiago Munín <santimunin at gmail.com>
Date:   Thu Jun 21 17:00:58 2018 -0400

    rts/linker/{SymbolExtras,elf_got}.c: map code as read-only
    
    protect mmaped addresses from writes after being initially manipulated
    
    Test Plan: ./validate
    
    Reviewers: bgamari, erikd, simonmar
    
    Reviewed By: bgamari
    
    Subscribers: angerman, carlostome, rwbarton, thomie, carter
    
    GHC Trac Issues: #14069
    
    Differential Revision: https://phabricator.haskell.org/D4817


>---------------------------------------------------------------

67c422ca0e7b94e021430e3dfc9b19f3de21ed16
 rts/linker/SymbolExtras.c | 8 ++++++--
 rts/linker/elf_got.c      | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/rts/linker/SymbolExtras.c b/rts/linker/SymbolExtras.c
index 486fa4a..88541f4 100644
--- a/rts/linker/SymbolExtras.c
+++ b/rts/linker/SymbolExtras.c
@@ -51,8 +51,9 @@ int ocAllocateSymbolExtras( ObjectCode* oc, int count, int first )
       n = roundUpToPage(oc->fileSize);
 
       /* Keep image and symbol_extras contiguous */
-      void *new = mmapForLinker(n + (sizeof(SymbolExtra) * count),
-                                MAP_ANONYMOUS, -1, 0);
+
+      size_t allocated_size = n + (sizeof(SymbolExtra) * count);
+      void *new = mmapForLinker(allocated_size, MAP_ANONYMOUS, -1, 0);
       if (new) {
           memcpy(new, oc->image, oc->fileSize);
           if (oc->imageMapped) {
@@ -62,6 +63,9 @@ int ocAllocateSymbolExtras( ObjectCode* oc, int count, int first )
           oc->imageMapped = true;
           oc->fileSize = n + (sizeof(SymbolExtra) * count);
           oc->symbol_extras = (SymbolExtra *) (oc->image + n);
+          if(mprotect(new, allocated_size, PROT_READ | PROT_EXEC) != 0) {
+              sysErrorBelch("unable to protect memory");
+          }
       }
       else {
           oc->symbol_extras = NULL;
diff --git a/rts/linker/elf_got.c b/rts/linker/elf_got.c
index 0395d16..10ea25b 100644
--- a/rts/linker/elf_got.c
+++ b/rts/linker/elf_got.c
@@ -62,6 +62,9 @@ makeGot(ObjectCode * oc) {
                     symTab->symbols[i].got_addr
                             = (uint8_t *)oc->info->got_start
                               + (slot++ * sizeof(void*));
+        if(mprotect(mem, oc->info->got_size, PROT_READ) != 0) {
+            sysErrorBelch("unable to protect memory");
+        }
     }
     return EXIT_SUCCESS;
 }