libelf: Fix deadlock in __libelf_readall

Apply locking during __libelf_readall.

Signed-off-by: Heather S. McIntyre <hsm2@rice.edu>
Signed-off-by: Aaron Merey <amerey@redhat.com>
Signed-off-by: Mark Wielaard <mark@klomp.org>

diff --git a/libelf/common.h b/libelf/common.h
index 9b2a856d118a55c0977bbc8d9978d8f6b42f18b3..8e33a70ebc53b1a70b8f056b81d83f6e95c4daae 100644 (file)
--- a/libelf/common.h
+++ b/libelf/common.h
@@ -89,30 +89,34 @@ allocate_elf (int fildes, void *map_address, int64_t offset, size_t maxsize,
 }
 
 
-/* Acquire lock for the descriptor and all children.  */
+/* Caller must hold a lock for ELF. If there are children then a lock
+   will be acquired for each of them (recursively).  */
 static void
 __attribute__ ((unused))
-libelf_acquire_all (Elf *elf)
+libelf_acquire_all_children (Elf *elf)
 {
-  rwlock_wrlock (elf->lock);
-
   if (elf->kind == ELF_K_AR)
     {
       Elf *child = elf->state.ar.children;
 
       while (child != NULL)
        {
+         rwlock_wrlock (child->lock);
+
          if (child->ref_count != 0)
-           libelf_acquire_all (child);
+           libelf_acquire_all_children (child);
+
          child = child->next;
        }
     }
 }
 
-/* Release own lock and those of the children.  */
+
+/* Caller must hold a lock for ELF. If there are children then a lock
+   will be released for each of them (recursively).  */
 static void
 __attribute__ ((unused))
-libelf_release_all (Elf *elf)
+libelf_release_all_children (Elf *elf)
 {
   if (elf->kind == ELF_K_AR)
     {
@@ -121,12 +125,12 @@ libelf_release_all (Elf *elf)
       while (child != NULL)
        {
          if (child->ref_count != 0)
-           libelf_release_all (child);
+           libelf_release_all_children (child);
+
+         rwlock_unlock (child->lock);
          child = child->next;
        }
     }
-
-  rwlock_unlock (elf->lock);
 }
 
 

diff --git a/libelf/elf_readall.c b/libelf/elf_readall.c
index d0f9a28cc59ea192165391babb31eed951a771ed..4ef8fe97c94074be274ea46c393191dc6ee912a8 100644 (file)
--- a/libelf/elf_readall.c
+++ b/libelf/elf_readall.c
@@ -84,7 +84,7 @@ __libelf_readall (Elf *elf)
 
       /* If this is an archive and we have derived descriptors get the
         locks for all of them.  */
-      libelf_acquire_all (elf);
+      libelf_acquire_all_children (elf);
 
       if (elf->maximum_size == ~((size_t) 0))
        {
@@ -141,7 +141,7 @@ __libelf_readall (Elf *elf)
        __libelf_seterrno (ELF_E_NOMEM);
 
       /* Free the locks on the children.  */
-      libelf_release_all (elf);
+      libelf_release_all_children (elf);
     }
 
   rwlock_unlock (elf->lock);