Re: [PATCH] aio: fix io_setup/io_destroy race

[Jeff Moyer]

Al Viro <viro@xxxxxxxxxxxxxxxxxx> writes:

> Have ioctx_alloc() return an extra reference, so that caller would drop it
> on success and not bother with re-grabbing it on failure exit.  The current
> code is obviously broken - io_destroy() from another thread that managed
> to guess the address io_setup() would've returned would free ioctx right
> under us; gets especially interesting if aio_context_t * we pass to
> io_setup() points to PROT_READ mapping, so put_user() fails and we end
> up doing io_destroy() on kioctx another thread has just got freed...

Al, you certainly are creative.  ;-) I agree with the problem and the
fix.  It would be nice, though if you had added comments.

I ran xfstests ./check -g aio, and there were no problems.

Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
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