jingfei195887 opened a new pull request, #21752:
URL: https://github.com/apache/nuttx/pull/21752
## Summary
POSIX error handling fixes for symlink(), unlink(), rmdir() and readlink()
on the pseudo file system.
- **fs/vfs: reject an empty symlink target.** `symlink("", path)` created a
link to "", which POSIX rejects with ENOENT. Any `inode_find()` failure
for path2 was also taken as "path2 does not exist"; only -ENOENT now leads
to creating the link.
- **fs/vfs: return EEXIST for symlink() over a link.** path2 was looked up
with the final link followed, so a dangling link at path2 was replaced
instead of failing with EEXIST.
- **fs/vfs: return EISDIR from unlink() of a directory.** `nx_unlink()`
removed an empty pseudo directory as if it were a file. POSIX does not
allow unlink() of a directory; `remove()` already falls back to
`rmdir()` on EISDIR.
- **fs/vfs: return EINVAL from rmdir() of "dir/.".** The lookup collapses
".", so `rmdir("dir/.")` removed dir. POSIX requires EINVAL when the last
component is dot.
- **fs/vfs: do not NUL-terminate readlink() output.** When the target did
not fit, the last byte of the buffer was a NUL instead of the next byte of
the target, although readlink() returned bufsize.
## Impact
`unlink()` of an empty pseudo directory now fails with EISDIR; `rmdir()`,
`remove()` and `rm -r` still remove it. Pseudo files, drivers and links
are unlinked as before.
## Testing
Host: Ubuntu x86_64, gcc (Ubuntu 13.1.0-8ubuntu1~22.04) 13.1.0, master
72c45233a0 (rebased onto 72c45233a0; no
new commit touches these files), `sim:nsh` with `CONFIG_FS_LINKS`. A small
test program:
| call | master | this PR |
|---|---|---|
| `symlink("", "/l")` | 0 | -1, ENOENT |
| `symlink("/etc", "/l")` with `/l` a dangling link | 0 | -1, EEXIST |
| `unlink("/d")` of an empty pseudo directory | 0, `/d` removed | -1,
EISDIR, `/d` kept |
| `rmdir("/tmp/d/.")` | 0, `/tmp/d` removed | -1, EINVAL, `/tmp/d` kept |
| `readlink()` of `/etc/group` into 4 bytes | 4, "/et\\0" | 4, "/etc" |
With `CONFIG_PSEUDOFS_FILE`, `unlink()` of a pseudo file and of a link,
and `remove()` of a pseudo directory, succeed on both master and this PR.
- `./tools/checkpatch.sh -g master..HEAD`: all checks pass.
- Make and CMake builds pass; `ostest` exits with status 0.
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