Perform pseudo-filesystem permission checks inside inode_reserve() and
inode_remove() while the inode tree lock is held, and hold that lock across
pseudorename mutations so symlink swaps cannot bypass directory checks.
Hold a read lock around pseudo-fs open permission checks.
On setuid/setgid exec, update saved set-IDs, mark the task group secure,
sanitize dangerous environment variables, clear debug/dumpable flags, and
add issetugid(), secure_getenv(), and PR_SET/GET_DUMPABLE support.
Signed-off-by: Abhishek Mishra <mishra.abhishek2808@gmail.com>
