Re: [PATCH] fs: Evaluate O_WRONLY | O_RDWR to O_RDWR

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On Thu, Dec 13, 2018 at 2:10 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Dec 13, 2018 at 05:57:17AM -0600, Goldwyn Rodrigues wrote:
> > A user can open(O_WRONLY | O_RDWR) and the options are valid.
> > However, OPEN_FMODE() evaluates both FMODE_READ and FMODE_WRITE,
> > as negative. We also need to protect the lower layers from this
> > anomaly.
> >
> > Solve it by dropping O_WRONLY, so O_RDWR takes precedence.
>
> Congratulations, you've broken fdutils...  Passing 3 in lower bits
> of open() flags is *not* the same as O_RDWR; behaiviour is
> different and deliberately chosen by existing userland code.
>
> IOW, NAK.

Yap, sorry, I missed FMODE_WRITE_IOCTL when I made this suggestion.
open mode 3 seems to be reserved to some special case of ioctl to floppy
block device.

I guess it would be simpler for you to accommodate for the special case
in ima_calc_file_hash() by masking out O_ACCMODE from flags before
adding O_RDONLY.

Thanks,
Amir.



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