Re: Symlinks and Cryogenic Sleep

From: Mark A. Heilpern (heilpernat_private)
Date: Mon Jan 03 2000 - 14:34:45 PST

  • Next message: Goetz Babin-Ebell: "Re: Symlinks and Cryogenic Sleep"

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    At 09:24 PM 1/3/00 +0100, you wrote:
    [snip]
    
    >When
    >the application reaches the critical section of code between the
    >lstat and the open, you stop it by sending it a SIGSTOP. You record
    >the device and inode number of your /tmp file, remove it, and wait.
    >
    >Seconds, days or maybe even weeks later, somebody creates an interesting
    >file with exactly the same inode (and device) number as the one you
    >used with my setuid program. You now create a symlink in /tmp, pointing
    >to that interesting file, and send my setuid application a SIGCONT.
    >Zap, there goes the file.
    [snip]
    >Comments? Suggestions?
    
    
    Maybe I'm just naive, but it's my understanding that you cannot send signals
    to a process you don't own unless you are root.
    
    On my Linux 2.2.13 system, I just tried sending SIGSTOP to a root-owned
    and nobody-owned process, and each time was told I was not the process owner.
    
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