From owner-freebsd-current  Thu Dec 24 08:04:57 1998
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Date: Thu, 24 Dec 1998 11:04:45 -0500 (EST)
From: Brian Feldman <green@unixhelp.org>
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To: current@FreeBSD.ORG
Subject: revoke of fifos
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revoke(2) on VFIFO types is broken now, leading to stranded mbuf's. I suppose
bde is tracking this down, but for now, why don't we return EINVAL in revoke(2)?

/usr/src/sys/kern/vfs_syscalls.c: unmodified, readonly: line 2912 of 3038 [95%] 
        if (vp->v_type == VFIFO) {
                error = EINVAL;
                goto out;
        }

That should temporarily work to prevent the following easily reproducible mbuf-
starvation crash case:
(as any user)
mkfifo fifo
while true; do dd if=fifo of=/dev/null & dd if=/dev/zero of=fifo & ./revoke \
fifo; done
where revoke.c is on the lines of

#include <stdio.h>
#include <unistd.h>

int
main(int argc, char **argv) {
        if (!argv[1])
                exit(1);
        printf("revoke(%s) == %d\n", argv[1], revoke(argv[1]));
        exit(0);
}


 Brian Feldman						  _ __  ___ ___ ___  
 green@unixhelp.org				      _ __ ___ | _ ) __|   \ 
		      http://www.freebsd.org/	 _ __ ___ ____ | _ \__ \ |) |
 FreeBSD: The Power to Serve!		   _ __ ___ ____ _____ |___/___/___/ 


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