elf: Handle non-directory name in search path (BZ 31035)

The open_path stops if a relative path in search path contains a
component that is a non directory (for instance, if the component
is an existing file).

For instance:

  $ cat > lib.c <<EOF
  > void foo (void) {}
  > EOF
  $ gcc -shared -fPIC -o lib.so lib.c
  $ cat > main.c <<EOF
  extern void foo ();
  int main () { foo (); return 0; }
  EOF
  $ gcc -o main main.c lib.so
  $ LD_LIBRARY_PATH=. ./main
  $ LD_LIBRARY_PATH=non-existing/path:. ./main
  $ LD_LIBRARY_PATH=$(pwd)/main:. ./main
  $ LD_LIBRARY_PATH=./main:. ./main
  ./main: error while loading shared libraries: lib.so: cannot open shared object file: No such file or directory

The invalid './main' should be ignored as a non-existent one,
instead as a valid but non accessible file.

Absolute paths do not trigger this issue because their status are
initialized as 'unknown' and open_path check if this is a directory.

Checked on x86_64-linux-gnu.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 2923b1141d..8d351153c8 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1810,7 +1810,6 @@ open_path (const char *name, size_t namelen, int mode,
       size_t cnt;
       char *edp;
       int here_any = 0;
-      int err;
 
       /* If we are debugging the search for libraries print the path
 	 now if it hasn't happened now.  */
@@ -1911,8 +1910,12 @@ open_path (const char *name, size_t namelen, int mode,
 	      return -1;
 	    }
 	}
-      if (here_any && (err = errno) != ENOENT && err != EACCES)
-	/* The file exists and is readable, but something went wrong.  */
+
+      /* Continue the search if the file does not exist (ENOENT), if it can
+	 not be accessed (EACCES), or if the a component in the path is not a
+	 directory (for instance, if the component is a existing file meaning
+	 essentially that the pathname is invalid - ENOTDIR).  */
+      if (here_any && errno != ENOENT && errno != EACCES && errno != ENOTDIR)
 	return -1;
 
       /* Remember whether we found anything.  */