[uclibc-ng-devel] [PATCH] dl-elf.c: Add null-pointer check

[Frank Mehnert]

Hi,

static analysis tools complain that the following code lacks a null-pointer
check:

ldso/ldso/dl-elf.c:

          /*
           * Add this object into the symbol chain
           */
          if (*rpnt
  #ifdef __LDSO_STANDALONE_SUPPORT__
                  /* Do not create a new chain entry for the main executable */
                  && (*rpnt)->dyn
  #endif
                  ) {
                  (*rpnt)->next = _dl_malloc(sizeof(struct dyn_elf));
                  _dl_memset((*rpnt)->next, 0, sizeof(struct dyn_elf));
                  (*rpnt)->next->prev = (*rpnt);
                  *rpnt = (*rpnt)->next;
          }
  #ifndef SHARED
          /* When statically linked, the first time we dlopen a DSO
           * the *rpnt is NULL, so we need to allocate memory for it,
           * and initialize the _dl_symbol_table.
           */
          else {
                  *rpnt = _dl_symbol_tables = _dl_malloc(sizeof(struct 
dyn_elf));
                  _dl_memset(*rpnt, 0, sizeof(struct dyn_elf));
          }
  #endif
          (*rpnt)->dyn = tpnt;
          ^^^^^^^^^^^^^^^^^^^^


There is a check for (*rpnt == NULL) right after the first comment but the
"else" case which performs an allocation does only exist if SHARED is not
defined. Otherwise it may happen (at least in theory) that *rpnt=NULL when
executing

  (*rpnt)->dyn = tpnt;


Proposed fix:

diff --git a/ldso/ldso/dl-elf.c b/ldso/ldso/dl-elf.c
index 8210a012e..3ba3144e2 100644
--- a/ldso/ldso/dl-elf.c
+++ b/ldso/ldso/dl-elf.c
@@ -900,7 +900,8 @@ struct elf_resolve *_dl_load_elf_shared_library(unsigned 
int rflags,
                _dl_memset(*rpnt, 0, sizeof(struct dyn_elf));
        }
 #endif
-       (*rpnt)->dyn = tpnt;
+       if (*rpnt)
+               (*rpnt)->dyn = tpnt;
        tpnt->usage_count++;
        if (tpnt->rtld_flags & RTLD_NODELETE)
                tpnt->usage_count++;



Kind regards

Frank


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