[pbs-devel] [PATCH proxmox 1/2] sys: adapt to IO Safety changes in rustc

[Fabian Grünbichler]

`OwnedFd`s are now (rustc 1.80+) checked for validity when dropped in a debug
build, to catch usage after closing. Unfortunately those checks don't account
for the special value `AT_FDCWD` (-100) which is not a "real" FD, but a magic
constant used by many libc functions to signify operations starting at the
current working directory.

changing our `cwd` helper to open the CWD for real, instead of just returning
the magic value that pretends to be an FD, works around those limitations with
the least API churn.

Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
---
technically the changed return type is a breaking change, but see next
patch..

 proxmox-sys/src/fd.rs     | 6 +++---
 proxmox-sys/src/fs/dir.rs | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/proxmox-sys/src/fd.rs b/proxmox-sys/src/fd.rs
index ad12e663..073dd08d 100644
--- a/proxmox-sys/src/fd.rs
+++ b/proxmox-sys/src/fd.rs
@@ -2,9 +2,9 @@
 
 use std::os::unix::io::AsRawFd;
 
-use nix::fcntl::OFlag;
 use nix::sys::stat::Mode;
 use nix::NixPath;
+use nix::{fcntl::OFlag, sys::stat};
 
 use std::os::unix::io::{FromRawFd, OwnedFd, RawFd};
 
@@ -23,8 +23,8 @@ pub fn change_cloexec(fd: RawFd, on: bool) -> Result<(), anyhow::Error> {
     Ok(())
 }
 
-pub fn cwd() -> OwnedFd {
-    unsafe { OwnedFd::from_raw_fd(libc::AT_FDCWD) }
+pub fn cwd() -> Result<OwnedFd, nix::Error> {
+    open(".", OFlag::O_DIRECTORY, stat::Mode::empty())
 }
 
 pub fn open<P>(path: &P, oflag: OFlag, mode: Mode) -> Result<OwnedFd, nix::Error>
diff --git a/proxmox-sys/src/fs/dir.rs b/proxmox-sys/src/fs/dir.rs
index 807a00ad..a7a95b02 100644
--- a/proxmox-sys/src/fs/dir.rs
+++ b/proxmox-sys/src/fs/dir.rs
@@ -120,7 +120,7 @@ fn create_path_do(
         }
         Some(Component::CurDir) => {
             let _ = iter.next();
-            crate::fd::cwd()
+            crate::fd::cwd()?
         }
         Some(Component::ParentDir) => {
             let _ = iter.next();
@@ -128,7 +128,7 @@ fn create_path_do(
         }
         Some(Component::Normal(_)) => {
             // simply do not advance the iterator, heavy lifting happens in create_path_at_do()
-            crate::fd::cwd()
+            crate::fd::cwd()?
         }
         None => bail!("create_path on empty path?"),
     };
-- 
2.39.2