Crash with SIGSYS due to illegal newfstatat system call about wob

[francma]

Thank you for pointing this out. I decided to roll my own fix because I don't like this part of int fstatat(int dirfd, const char *pathname, struct stat *buf, int flags); syscall:

If pathname is absolute, then dirfd is ignored.

Allowing fstating anything on filesystem.

I also tried restricting fstatat with seccomp rule like this:

rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(read), 3,
                            SCMP_A0(SCMP_CMP_EQ, fd),
                            SCMP_A1(SCMP_CMP_EQ, (scmp_datum_t)buf),
                            SCMP_A2(SCMP_CMP_LE, BUF_SIZE));

To allow only empty string ("") as second fstatat argument, but as that empty string is passed as pointer I could only compare it to that pointer (which is random). More explanation in article Deep argument inspection for seccomp on lwm.net