Messages in this thread | | | Date | Fri, 20 May 2022 16:15:16 +0000 | From | Al Viro <> | Subject | Re: [PATCH v4 0/3] random: convert to using iters, for Al Viro |
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On Fri, May 20, 2022 at 09:53:30AM -0600, Jens Axboe wrote: > On 5/20/22 9:47 AM, Al Viro wrote: > > On Fri, May 20, 2022 at 09:34:46AM -0600, Jens Axboe wrote: > > > >> I'm very sure, otherwise we're just accepting that we're breaking real > >> world applications. > > > > "Breaking" as in "it used to work with earlier kernels, doesn't work with > > recent ones"? Details, please... > > Yes, as in exactly that. This is what drove this addition of > ->read_iter() for urandom. See commit: > > ommit 36e2c7421f02a22f71c9283e55fdb672a9eb58e7 > Author: Christoph Hellwig <hch@lst.de> > Date: Thu Sep 3 16:22:34 2020 +0200 > > fs: don't allow splice read/write without explicit ops > > related to the set_fs() changes, and now go look for any commit that > has: > > Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops") > > in it and see that this isn't an isolated incident at all. > > tldr - splice from /dev/urandom used to work, and I recently got a > report internally on an application that broke on upgrade from 5.6 to > 5.12 exactly because it now just just -EINVAL's instead.
IIRC, Linus' position at the time had been along the lines of "splice is not so good ABI anyway, so let's do it and fix up the places that do get real-world complaints once such appear". So /dev/urandom is one such place...
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