Re: [PATCH] new syscall: flink

[daw@mozart.cs.berkeley.edu (David Wagner)]

H. Peter Anvin wrote:
>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

You're right!  Good point. I retract the comments in my previous email.
(I did try an experiment like this, but apparently not the right one.)

My conclusion: /proc/*/fd is a security hole.  It should be fixed.
Do you agree?