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vhost_user_fs: Use a fd for /proc/self/fd instead of /proc

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Open a file descriptor to /proc/self/fd instead of /proc. We aren't
using any other entries from that directory, and doing this allows us
to keep working even if /proc is no longer present in our
namespace (useful for sandboxing).

Signed-off-by: Sergio Lopez <slp@redhat.com>
This commit is contained in:
Sergio Lopez 2020-04-24 12:45:56 +02:00 committed by Sebastien Boeuf
parent ba4ec7fce2
commit 831cff3fee
1 changed files with 13 additions and 13 deletions
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26
vhost_user_fs/src/passthrough.rs
View File

@ -28,7 +28,7 @@ use crate::multikey::MultikeyBTreeMap;
const CURRENT_DIR_CSTR: &[u8] = b".\0";
const PARENT_DIR_CSTR: &[u8] = b"..\0";
const EMPTY_CSTR: &[u8] = b"\0";
const PROC_CSTR: &[u8] = b"/proc\0";
const PROC_CSTR: &[u8] = b"/proc/self/fd\0";
type Inode = u64;
type Handle = u64;
@ -271,11 +271,11 @@ pub struct PassthroughFs {
handles: RwLock<BTreeMap<Handle, Arc<HandleData>>>,
next_handle: AtomicU64,
// File descriptor pointing to the `/proc` directory. This is used to convert an fd from
// File descriptor pointing to the `/proc/self/fd` directory. This is used to convert an fd from
// `inodes` into one that can go into `handles`. This is accomplished by reading the
// `self/fd/{}` symlink. We keep an open fd here in case the file system tree that we are meant
// to be serving doesn't have access to `/proc`.
proc: File,
// `/proc/self/fd/{}` symlink. We keep an open fd here in case the file system tree that we are
// meant to be serving doesn't have access to `/proc/self/fd`.
proc_self_fd: File,
// Whether writeback caching is enabled for this directory. This will only be true when
// `cfg.writeback` is true and `init` was called with `FsOptions::WRITEBACK_CACHE`.
@ -302,7 +302,7 @@ impl PassthroughFs {
}
// Safe because we just opened this fd.
let proc = unsafe { File::from_raw_fd(fd) };
let proc_self_fd = unsafe { File::from_raw_fd(fd) };
Ok(PassthroughFs {
inodes: RwLock::new(MultikeyBTreeMap::new()),
@ -311,7 +311,7 @@ impl PassthroughFs {
handles: RwLock::new(BTreeMap::new()),
next_handle: AtomicU64::new(0),
proc,
proc_self_fd,
writeback: AtomicBool::new(false),
cfg,
@ -319,7 +319,7 @@ impl PassthroughFs {
}
pub fn keep_fds(&self) -> Vec<RawFd> {
vec![self.proc.as_raw_fd()]
vec![self.proc_self_fd.as_raw_fd()]
}
fn open_inode(&self, inode: Inode, mut flags: i32) -> io::Result<File> {
@ -331,7 +331,7 @@ impl PassthroughFs {
.map(Arc::clone)
.ok_or_else(ebadf)?;
let pathname = CString::new(format!("self/fd/{}", data.file.as_raw_fd()))
let pathname = CString::new(format!("{}", data.file.as_raw_fd()))
.map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
// When writeback caching is enabled, the kernel may send read requests even if the
@ -359,7 +359,7 @@ impl PassthroughFs {
// to follow the `/proc/self/fd` symlink to get the file.
let fd = unsafe {
libc::openat(
self.proc.as_raw_fd(),
self.proc_self_fd.as_raw_fd(),
pathname.as_ptr(),
(flags | libc::O_CLOEXEC) & (!libc::O_NOFOLLOW),
)
@ -1065,7 +1065,7 @@ impl FileSystem for PassthroughFs {
let fd = hd.file.write().unwrap().as_raw_fd();
Data::Handle(hd, fd)
} else {
let pathname = CString::new(format!("self/fd/{}", inode_data.file.as_raw_fd()))
let pathname = CString::new(format!("{}", inode_data.file.as_raw_fd()))
.map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
Data::ProcPath(pathname)
};
@ -1076,7 +1076,7 @@ impl FileSystem for PassthroughFs {
match data {
Data::Handle(_, fd) => libc::fchmod(fd, attr.st_mode),
Data::ProcPath(ref p) => {
libc::fchmodat(self.proc.as_raw_fd(), p.as_ptr(), attr.st_mode, 0)
libc::fchmodat(self.proc_self_fd.as_raw_fd(), p.as_ptr(), attr.st_mode, 0)
}
}
};
@ -1162,7 +1162,7 @@ impl FileSystem for PassthroughFs {
let res = match data {
Data::Handle(_, fd) => unsafe { libc::futimens(fd, tvs.as_ptr()) },
Data::ProcPath(ref p) => unsafe {
libc::utimensat(self.proc.as_raw_fd(), p.as_ptr(), tvs.as_ptr(), 0)
libc::utimensat(self.proc_self_fd.as_raw_fd(), p.as_ptr(), tvs.as_ptr(), 0)
},
};
if res < 0 {