From a1885e2dc2a8f1c79ead4e6ceca1a53827b89048 Mon Sep 17 00:00:00 2001 From: Jim Meyering Date: Fri, 8 Oct 2010 18:42:59 +0200 Subject: 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. --- lib/fdopendir.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'lib/fdopendir.c') diff --git a/lib/fdopendir.c b/lib/fdopendir.c index 4adef63791..59826ae4aa 100644 --- a/lib/fdopendir.c +++ b/lib/fdopendir.c @@ -140,10 +140,23 @@ fd_clone_opendir (int fd) dir = opendir (name); saved_errno = errno; # else /* !REPLACE_FCHDIR */ + + /* Occupy the destination FD slot, so that save_cwd cannot hijack it. */ + int fd_reserve = dup (fd); + if (fd_reserve < 0) + { + saved_errno = errno; + dir = NULL; + goto fail; + } + struct saved_cwd saved_cwd; if (save_cwd (&saved_cwd) != 0) openat_save_fail (errno); + /* Liberate the target file descriptor, so that opendir uses it. */ + close (fd_reserve); + if (fchdir (fd) != 0) { dir = NULL; @@ -162,6 +175,7 @@ fd_clone_opendir (int fd) # endif /* !REPLACE_FCHDIR */ } + fail: if (proc_file != buf) free (proc_file); errno = saved_errno; -- cgit v1.2.1