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fget_unlocked() and fhold(). On sufficiently large machine, f_count can be legitimately very large, e.g. malicious code can dup same fd up to the per-process filedescriptors limit, and then fork as much as it can. On some smaller machine, I see kern.maxfilesperproc: 939132 kern.maxprocperuid: 34203 which already overflows u_int. More, the malicious code can create transient references by sending fds over unix sockets. I realized that this check is missed after reading https://secfault-security.com/blog/FreeBSD-SA-1902.fd.html Reviewed by: markj (previous version), mjg Tested by: pho (previous version) Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D20947
FreeBSD Source:
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include System include files.
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