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feat(hypercall): introduce chdir and uhyve mountpoint restrictions #1485

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feat(hypercall): introduce chdir and uhyve mountpoint restrictions #1485

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5a149dc
feat(uhyve): change mountpoint env var
n0toose Nov 27, 2024
8a673f3
feat(hypercall): proof of concept for chdir
n0toose Dec 1, 2024
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29 changes: 28 additions & 1 deletion src/fs/uhyve.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,7 @@ const UHYVE_PORT_OPEN: u16 = 0x440;
const UHYVE_PORT_CLOSE: u16 = 0x480;
const UHYVE_PORT_READ: u16 = 0x500;
const UHYVE_PORT_LSEEK: u16 = 0x580;
const UHYVE_PORT_CHDIR: u16 = 0x820;
const UHYVE_PORT_UNLINK: u16 = 0x840;

#[repr(C, packed)]
Expand Down Expand Up @@ -142,6 +143,22 @@ impl SysLseek {
}
}

#[repr(C, packed)]
struct SysChdir {
name: PhysAddr,
ret: i32,
}

impl SysChdir {
fn new(name: VirtAddr) -> SysChdir {
SysChdir {
name: paging::virtual_to_physical(name).unwrap(),
ret: -1,
}
}
}


#[repr(C, packed)]
struct SysUnlink {
name: PhysAddr,
Expand Down Expand Up @@ -321,7 +338,17 @@ impl VfsNode for UhyveDirectory {
pub(crate) fn init() {
info!("Try to initialize uhyve filesystem");
if is_uhyve() {
let mount_point = hermit_var_or!("UHYVE_MOUNT", "/root").to_string();
// TODO: Use FDT instead?
let mut mount_point = hermit_var_or!("UHYVE_MOUNTPOINT", "/root").to_string();
if ["/tmp", "/proc", ".", ".."].iter().any(|path| mount_point.starts_with(*path)) {
error!("UHYVE_MOUNTPOINT {} invalid, falling back to /root and informing host...", mount_point);
mount_point = "/root".to_owned();
let mut syschdir: SysChdir = SysChdir::new(VirtAddr::from_ptr(mount_point.as_ptr()));
uhyve_send(UHYVE_PORT_CHDIR, &mut syschdir);
if syschdir.ret != 0 {
panic!("Could not change invalid mount point to /root");
}
}
info!("Mounting uhyve filesystem at {}", mount_point);
fs::FILESYSTEM
.get()
Expand Down
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