fdopendir: fix a bug on systems lacking openat and /proc support

[gnulib.git] / ChangeLog

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+2010-10-08  Jim Meyering  <meyering@redhat.com>
+
+       fdopendir: fix a bug on systems lacking openat and /proc support
+       OpenBSD 4.7 is one such system.  The most noticeable effect was
+       failure of any application making nontrivial use of fts: rm, du,
+       chown, chmod etc.  E.g., "mkdir -p a/b; ./rm -rf a" would fail with
+         ./rm: traversal failed: `a': Bad file descriptor
+       Debugging that, you see that even though FD 6 was closed just
+       prior to the opendir call in fd_clone_opendir, its resulting
+       dir->dd_fd was 8, rather than the expected value of 6:
+
+       Breakpoint 3, fdopendir_with_dup (fd=6, older_dupfd=-1) at fdopendir.c:93
+       93                close (fd);
+       (gdb) n
+       94                dir = fd_clone_opendir (dupfd);
+       (gdb) n
+       95                saved_errno = errno;
+       (gdb) p dir->dd_fd
+       $11 = 8
+
+       Notice how it closes FD 6, then gets a DIR* pointer using FD 8.
+       The problem is that on OpenBSD, fd_clone_opendir has to resort
+       to using the old-style save/restore CWD mechanism, due to its
+       lack of openat/proc support, and *that* would steal the FD (6)
+       that opendir was supposed to use.
+
+       The fix is to squirrel away the desired FD so that save_cwd uses a
+       different one, and then free the dest FD right before calling opendir.
+       That guarantees opendir will use the required file descriptor.
+
+       * lib/fdopendir.c (fd_clone_opendir): Handle the above.
+
 2010-10-08  Bruno Haible  <bruno@clisp.org>
 
        sys_select: Avoid warning due to undeclared memset() on OpenBSD 4.5.