Messages in this thread | ![/](/images/icornerl.gif) | | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] new syscall: flink | Date | 6 Apr 2003 22:25:51 -0700 |
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Followup to: <b6qo2a$ecl$1@cesium.transmeta.com> By author: "H. Peter Anvin" <hpa@zytor.com> In newsgroup: linux.dev.kernel > > This, I believe, is the real issue. However, we already have that > problem: >
[Sample code]
Here is a better piece of sample code that actually shows a permissions violation happening:
[...] mkdir("testdir", 0700) = 0 open("testdir/testfile", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3 write(3, "Ansiktsburk\n", 12) = 12 close(3) = 0 open("testdir/testfile", O_RDONLY) = 3 chmod("testdir", 0) = 0 open("/proc/self/fd/3", O_RDWR) = 4 write(4, "Tjo fidelittan hatt!\n", 21) = 21 exit_group(0) = ?
----snip----
#include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <fcntl.h> #include <limits.h>
int main(int argc, char *argv[]) { int sfd, rfd, wfd; char filebuf[PATH_MAX];
mkdir("testdir", 0700);
/* Create the file legitimately */ sfd = open("testdir/testfile", O_WRONLY|O_CREAT|O_TRUNC, 0666); write(sfd, "Ansiktsburk\n", 12); close(sfd);
/* Open read-only file descriptor */ rfd = open("testdir/testfile", O_RDONLY);
/* Make directory inaccessible */ chmod("testdir", 0);
/* Open read-write file descriptor */ sprintf(filebuf, "/proc/self/fd/%d", rfd); wfd = open(filebuf, O_RDWR);
/* Clobber file */ write(wfd, "Tjo fidelittan hatt!\n", 21);
return 0; } -- <hpa@transmeta.com> at work, <hpa@zytor.com> in private! "Unix gives you enough rope to shoot yourself in the foot." Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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