fix(container): improve sandbox runtime compatibility by fslongjin · Pull Request #1981 · DragonOS-Community/DragonOS

fslongjin · 2026-06-16T03:18:20Z

Summary

Improve container-oriented mount and filesystem compatibility, including debugfs/mqueue mounts, mount/pivot-root behavior, overlayfs copy-up/path handling, and per-open backing-file reads.
Extend FUSE/virtiofs compatibility with xattr list/remove syscall coverage, FUSE xattr protocol handling, lookup caching, mmap/readaround behavior, and virtiofs smoke coverage.
Improve process/runtime behavior exercised by sandbox workloads, including PTY/TTY handling, pipe wakeups, eventfd pending-signal behavior, signal/ucontext handling, process exit cleanup, and x86_64 exec-entry ABI initialization.
Clear x86_64 %rdx on successful exec so glibc does not inherit the old execve() envp pointer as rtld_fini.
Fix N_TTY canonical input handling so PTY slave reads correctly treat newline as a canonical line delimiter after ICANON termios updates.
Add focused dunitest coverage for FUSE, overlayfs, PTY/pipe exec chains, eventfd, exec ABI, N_TTY canonical reads, and virtiofs smoke paths.

Root Cause

Sandbox workloads combine overlayfs, FUSE/virtiofs-backed lower layers, PTY/pipe based exec I/O, signal delivery, and Linux-compatible exec ABI expectations. Several DragonOS paths diverged from Linux behavior:

Some overlayfs/VFS reads operated through inode-level state instead of the opened backing file, which could bypass per-open filesystem state required by FUSE.
FUSE/virtiofs xattr list/remove behavior and ENOSYS-to-EOPNOTSUPP handling were incomplete.
PTY, pipe, eventfd, signal, and process cleanup paths had gaps that sandbox exec flows can expose.
N_TTY termios-derived state did not rebuild the character map for ICANON, ICRNL, and INLCR, so a PTY slave could receive line\n without advancing canon_head or waking canonical readers.
x86_64 exec did not clear %rdx before entering a new ELF image, while Linux clears regs->dx through ELF_PLAT_INIT; glibc treats %rdx at _start as rtld_fini.

Validation

git diff --check
make fmt
make kernel
make -C user/apps/tests/dunitest build-suites
Host dunitest: normal/exec_abi, normal/tty_pty_hangup, normal/pipe_waitqueue_wakeup
DragonOS guest dunitest: normal/exec_abi, normal/tty_pty_hangup, normal/pipe_waitqueue_wakeup, normal/pipe_release_wakeup
DragonOS guest with host virtiofsd: normal/virtiofs_smoke
CubeSandbox busybox smoke: sandbox creation succeeds; non-interactive ls and repeated uname -a execs exit successfully.

Notes

The latest PTY canonical-read hang was traced to N_TTY termios character-map handling rather than CubeSandbox, virtiofs, generic pipe wakeups, or the scheduler. The fix keeps the responsibility inside the line discipline and matches Linux N_TTY character-map semantics for canonical input.

Signed-off-by: longjin <longjin@dragonos.org>

fslongjin · 2026-06-16T06:02:18Z

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chatgpt-codex-connector · 2026-06-16T06:11:29Z

+            let new_backing_file = Arc::new(File::new(
+                current_inode.clone(),
+                Self::backing_open_flags(flags),
+            )?);


不要在 I/O 时重绑 overlay backing

当 lower-only 文件已被一个 fd 以 O_RDONLY 打开后，另一个 fd 以写入或截断方式打开会触发 copy-up；已打开的 fd 应继续使用打开时选定的 lower realfile。这里在后续 I/O 发现 current_inode 变成 upper 后重新 File::new 并替换 backing，导致旧 fd 的 read/mmap/flush 开始看到 upper 的新内容或截断结果，破坏打开文件描述的稳定语义；应保留 open 时的 backing，至少不要对既有只读 fd 自动切换。

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chatgpt-codex-connector · 2026-06-16T06:11:29Z

                return Err(SystemError::ENODEV);
            }
-            self.invalidate_clean_page_cache()?;
+            self.discard_clean_page_cache();


继续解除 FUSE direct-io mmap 的旧映射

当同一个 FUSE 文件已有普通 page-cache mmap 后，再通过返回 FOPEN_DIRECT_IO 的句柄做私有 mmap，原路径会先 unmap_mapping_pages() 再丢弃 clean cache。这里改为只调用 discard_clean_page_cache()，不会 zap 已映射的 PTE，旧 VMA 仍可访问旧 page-cache 页，而新的 direct-io mmap/fault 可能走另一份数据，造成同一文件页的陈旧或不一致映射；请在 direct-io mmap 前继续解除旧映射或复用原来的失效流程。

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fslongjin · 2026-06-17T07:50:29Z

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Signed-off-by: longjin <longjin@dragonos.org>

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chatgpt-codex-connector · 2026-06-17T07:59:58Z

+        init_info.auxv.insert(AtType::Uid as u8, 0);
+        init_info.auxv.insert(AtType::EUid as u8, 0);
+        init_info.auxv.insert(AtType::Gid as u8, 0);
+        init_info.auxv.insert(AtType::EGid as u8, 0);


使用真实凭据填充 auxv UID/GID

在非 root 进程执行 exec 时，这里会把 AT_UID/AT_EUID/AT_GID/AT_EGID 全部暴露为 0，导致用户态通过 getauxval() 看到自己是 root；glibc 或运行时可能依赖这些 auxv 值做权限和安全路径判断。这里应从当前进程的凭据填入真实/有效 uid、gid，而不是固定写 0。

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Signed-off-by: longjin <longjin@dragonos.org>

fslongjin · 2026-06-21T03:44:57Z

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Signed-off-by: longjin <longjin@dragonos.org>

fs: improve container mount filesystem semantics

7fb6780

Signed-off-by: longjin <longjin@dragonos.org>

github-actions Bot added the ambiguous The title of PR/issue doesn't match the format label Jun 16, 2026

fix overlayfs open file semantics for containers

f46da9e

Signed-off-by: longjin <longjin@dragonos.org>

github-actions Bot added the test Unitest/User space test label Jun 16, 2026

fslongjin marked this pull request as ready for review June 16, 2026 06:02

chatgpt-codex-connector Bot reviewed Jun 16, 2026

View reviewed changes

fix(container): improve sandbox runtime compatibility

809e239

Signed-off-by: longjin <longjin@dragonos.org>

fslongjin force-pushed the codex/container-mount-fs-semantics branch from 2b82b9d to 809e239 Compare June 17, 2026 07:51

fslongjin changed the title ~~[codex] improve container mount filesystem semantics~~ fix(container): improve sandbox runtime compatibility Jun 17, 2026

github-actions Bot added Bug fix A bug is fixed in this pull request and removed ambiguous The title of PR/issue doesn't match the format labels Jun 17, 2026

chatgpt-codex-connector Bot reviewed Jun 17, 2026

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fslongjin added 9 commits June 17, 2026 08:11

fix(process): sync fork arch state through arch hook

defee30

Signed-off-by: longjin <longjin@dragonos.org>

fix(mm): zap private COW mappings on truncate

33cd4a1

Signed-off-by: longjin <longjin@dragonos.org>

fix(tty): rebuild n_tty char map for canonical mode

ee01e24

Signed-off-by: longjin <longjin@dragonos.org>

fix(process): harden fork publication ordering

c1a7be0

Signed-off-by: longjin <longjin@dragonos.org>

fix: apply staged compatibility updates

a71e9f3

Signed-off-by: longjin <longjin@dragonos.org>

fix(mm): defer file mmap publication until hook succeeds

b7c52e7

Signed-off-by: longjin <longjin@dragonos.org>

fix(fat): cache negative directory lookups

8afb8eb

Signed-off-by: longjin <longjin@dragonos.org>

docs: remove accidental PR documents

22c1f01

Signed-off-by: longjin <longjin@dragonos.org>

fix(vfs): harden filesystem state transitions

50b3348

Signed-off-by: longjin <longjin@dragonos.org>

chatgpt-codex-connector Bot reviewed Jun 21, 2026

View reviewed changes

Comment thread kernel/src/filesystem/vfs/syscall/xattr_utils.rs

fix(ext4): wire xattr list and remove ops

d3a1c27

Signed-off-by: longjin <longjin@dragonos.org>

fslongjin merged commit 69ee213 into DragonOS-Community:master Jun 21, 2026
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fix(container): improve sandbox runtime compatibility#1981

fix(container): improve sandbox runtime compatibility#1981
fslongjin merged 13 commits into
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