[PATCH resend] sed: check errors writing file with sed -i

[Denys Vlasenko]

Applied, thank you!

On Tue, Sep 19, 2023 at 10:11 AM Dominique Martinet
<asmadeus at codewreck.org> wrote:
>
> From: Dominique Martinet <dominique.martinet at atmark-techno.com>
>
> sed would currently not error if write failed when modifying a file.
>
> This can be reproduced with the following 'script':
> $ sudo mount -t tmpfs tmpfs -o size=1M /tmp/m
> $ sudo chmod 777 /tmp/m
> $ echo foo > /tmp/m/foo
> $ dd if=/dev/zero of=/tmp/m/fill bs=4k
> dd: error writing '/tmp/m/fill': No space left on device
> 256+0 records in
> 255+0 records out
> 1044480 bytes (1.0 MB, 1020 KiB) copied, 0.00234567 s, 445 MB/s
> $ busybox sed -i -e 's/.*/bar/' /tmp/m/foo
> $ echo $?
> 0
> $ cat /tmp/m/foo
> <empty>
>
> new behaviour:
> $ echo foo > /tmp/m/foo
> $ ./busybox sed -i -e 's/.*/bar/' /tmp/m/foo
> sed: write error
> $ echo $?
> 4
> $ cat /tmp/m/foo
> foo
>
> function                                             old     new   delta
> sed_main                                             754     801     +47
> ------------------------------------------------------------------------------
> (add/remove: 0/0 grow/shrink: 1/0 up/down: 47/0)               Total: 47 bytes
>    text    data     bss     dec     hex filename
>   75727    2510    1552   79789   137ad busybox_old
>   75774    2510    1552   79836   137dc busybox_unstripped
>
> Signed-off-by: Dominique Martinet <dominique.martinet at atmark-techno.com>
> ---
> Resending this patch again as it doesn't seem to have been applied.
>
> FWIW it's still applied on alpine builds (since Nov last year); would be
> great to see this merged so I can forget about it :)
>
>  editors/sed.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/editors/sed.c b/editors/sed.c
> index 00dde60be329..6179c5e80958 100644
> --- a/editors/sed.c
> +++ b/editors/sed.c
> @@ -1648,6 +1648,11 @@ int sed_main(int argc UNUSED_PARAM, char **argv)
>                         fchown(nonstdoutfd, statbuf.st_uid, statbuf.st_gid);
>
>                         process_files();
> +                       fflush(G.nonstdout);
> +                       if (ferror(G.nonstdout)) {
> +                               xfunc_error_retval = 4;  /* It's what gnu sed exits with... */
> +                               bb_simple_error_msg_and_die(bb_msg_write_error);
> +                       }
>                         fclose(G.nonstdout);
>                         G.nonstdout = stdout;
>
> --
> 2.39.2
>