bug#70877: guix-daemon fails to copy 4+GB file to store

[Efraim Flashner <efraim@flashner.co.il>]

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On Sat, May 11, 2024 at 12:52:53PM +0200, Ricardo Wurmus wrote:
> The guix-daemon's libutil/util.cc uses copy_file_range to copy a
> downloaded file into the store.  copy_file_range fails on files larger
> than 4GB with an error like this:
> 
>     guix build: error: short write in copy_file_range `15' to `16': No such file or directory
> 
> The man page for copy_file_range says that it could return EFBIG when
> the range exceeds the maximum range.  The daemon code does not check any
> limits and will attempt to copy the whole file.
> 
> I believe our code ought to check the value of st.size and fall back to
> a boring copy if it exceeds some "reasonable" value.
> 
> This is where copy_file_range is used:
> https://git.savannah.gnu.org/cgit/guix.git/tree/nix/libutil/util.cc#n382
> 
> Here is a little reproducer:
> 

> (use-modules (guix download)
>              (guix packages)
>              (guix build-system trivial))
> 
> (package
>   (name "chungus")
>   (version "1")
>   (source
>    (origin
>      (method url-fetch)
>      (uri "http://localhost:1111/chungus")
>      (sha256
>       (base32 "0nx67d4ls2nfwcfdmg81vf240z6lpwpdqypssr1wzn3hyz4szci4"))))
>   (build-system trivial-build-system)
>   (home-page "")
>   (synopsis "")
>   (description "")
>   (license #f))

> 
> --8<---------------cut here---------------start------------->8---
> # generate a big file
> dd bs=1M count=4096 if=/dev/zero of=/tmp/chungus
> # serve it
> guix shell woof -- woof -i 127.0.0.1 -p 1111 -c 1 /tmp/chungus
> # build the source derivation
> guix build --no-grafts -Sf bug.scm
> # observe the error
> # guix build: error: short write in copy_file_range `15' to `16': No such file or directory
> --8<---------------cut here---------------end--------------->8---
> 

This sounds like a similar failure to bug 65714 that I ran into with
guix copy, but I wasn't able to diagnose it.

https://issues.guix.gnu.org/65714


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Efraim Flashner   <efraim@flashner.co.il>   רנשלפ םירפא
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