RFR: 8357425: (fs) SecureDirectoryStream setPermissions should use fchmodat

[Alan Bateman]

On Thu, 29 May 2025 23:37:26 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

> Modify to use the `fchmodat(2)` system call to set permissions where possible to do so. This fixes the problem presented in the issue description.

src/java.base/unix/classes/sun/nio/fs/UnixSecureDirectoryStream.java line 423:

> 421:                 else if (fchmodatNoFollowSupported())
> 422:                     fchmodat(dfd, file, UnixFileModeAttribute.toUnixMode(perms),
> 423:                              AT_SYMLINK_NOFOLLOW);

The 4 cases look okay. If you adds`int mode = UnixFileModeAttribute.toUnixMode(perms)` then it would avoid the repeated code and avoid the line splits, just makes it easier to read.

src/java.base/unix/classes/sun/nio/fs/UnixSecureDirectoryStream.java line 434:

> 432:                 }
> 433:             } catch (UnixException x) {
> 434:                 x.rethrowAsIOException(file);

'file' will be null when changing the directory's permission, can you double check that case?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25534#discussion_r2115172005
PR Review Comment: https://git.openjdk.org/jdk/pull/25534#discussion_r2115172441