[gl-agnx]

Change

Fix the actual CodeQL TOCTOU report at server/main.c:87 in parent PR #2 (check115329964830). No suppression is added.

• Open the host-seed parent directory once with O_DIRECTORY/O_NOFOLLOW, then validate the opened inode with fstat (owner and non-group/other-write mode).
• Use that held descriptor for seed openat, exclusive creation, concurrent-creator retry, unlinkat failure cleanup and directory fsync. Renaming/replacing the pathname after validation cannot redirect these operations.
• Strip redundant trailing parent separators before O_NOFOLLOW; reject invalid final names and avoid FIFO blocking before regular-file validation.
• Preserve the 32-byte seed format and existing private ownership/mode checks. A completed seed survives directory-fsync failure while the invocation fails, preserving identity for retry.

Validation

24 isolated Linux synthetic fixtures passed. The harness extracts the actual production random_seed/host_seed functions and compiles only those with -std=c99 -Wall -Wextra -Werror -O2. It does not build or launch the daemon.

Coverage includes existing-key reuse, deterministic parent-path swaps during reuse/create/write-error cleanup, symlink parent (including repeated separators), seed symlink/FIFO/directory/length/mode/owner rejection, concurrent creator, short/EINTR I/O, entropy/read/write/file-fsync/close errors, and directory-fsync failure retaining the complete identity.

No real keys were accessed or exported. No full source/CMake/Yocto/Vivado build, board/network/UART/JTAG access, manual CI dispatch, merge, or recipe/source-pin change was performed. Automatic PR checks must confirm CodeQL disposition; focused fixtures are not full-server or board qualification.

Stack and deployment

Base feat/mpunoxv-interactive-sshd at a397eb9 (parent PR #2). Keep the existing BSP source pins and board binary until a separately built successor is tested. Existing persistent host seed is reused; no rekeying/migration is required.