Fix calling proc_self_status() more than once. (#995)

Fix `proc_self_status()` to reset the directory cursor before iterating
through the directory entries when searching for bind mounts. This fixes
a failure when called more than once, due to the cursor being left at
the end.

Fixes #994.

src/procfs.rs

@@ -21,8 +21,8 @@
 use crate::fd::{AsFd, BorrowedFd, OwnedFd};
 use crate::ffi::CStr;
 use crate::fs::{
-    fstat, fstatfs, major, openat, renameat, FileType, FsWord, Mode, OFlags, RawDir, Stat, CWD,
-    PROC_SUPER_MAGIC,
+    fstat, fstatfs, major, openat, renameat, seek, FileType, FsWord, Mode, OFlags, RawDir,
+    SeekFrom, Stat, CWD, PROC_SUPER_MAGIC,
 };
 use crate::io;
 use crate::path::DecInt;
@@ -488,6 +488,9 @@ fn open_and_check_file(
     let mut found_file = false;
     let mut found_dot = false;
 
+    // Position the directory iteration at the start.
+    seek(dir, SeekFrom::Start(0))?;
+
     let mut buf = [MaybeUninit::uninit(); 2048];
     let mut iter = RawDir::new(dir, &mut buf);
     while let Some(entry) = iter.next() {

tests/procfs/basic.rs

@@ -6,3 +6,11 @@ fn test_proc_self() {
     let fd = rustix::procfs::proc_self_fd().unwrap();
     assert_ne!(fd.as_raw_fd(), 0);
 }
+
+#[test]
+fn test_status_twice() {
+    let fd = rustix::procfs::proc_self_status().unwrap();
+    drop(fd);
+    let fd = rustix::procfs::proc_self_status().unwrap();
+    drop(fd);
+}