Re: [RFC PATCH] fs: introduce mkdirat2 syscall for atomic mkdir

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On Sat, Feb 27, 2021 at 09:26:21PM -0500, Drew DeVault wrote:
> On Sat Feb 27, 2021 at 9:24 PM EST, Matthew Wilcox wrote:
> > Where's the problem? If mkdir succeeds in a sticky directory, others
> > can't remove or rename it. So how can an app be tricked into doing
> > something wrong?
> 
> It's not a security concern, it's just about about making the software
> more robust.
> 
> 1. Program A creates a directory
> 2. Program A is pre-empted
> 3. Program B deletes the directory
> 4. Program A creates a file in that directory
> 5. RIP

umm ... program B deletes the directory.  program A opens it in order to
use openat().  program A gets ENOENT and exits, confused.  that's the
race you're removing here -- and it seems fairly insignificant to me.



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