linux-kernel - Re: [PATCH v14 08/17] splice: Do splice read from a file without using ITER

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Message-ID: <732891.1676670463@warthog.procyon.org.uk>
Date:   Fri, 17 Feb 2023 21:47:43 +0000
From:   David Howells <dhowells@...hat.com>
To:     Alexander Egorenkov <egorenar@...ux.ibm.com>
Cc:     dhowells@...hat.com, axboe@...nel.dk, david@...hat.com,
        hch@...radead.org, hch@....de, hdanton@...a.com, jack@...e.cz,
        jgg@...dia.com, jhubbard@...dia.com, jlayton@...nel.org,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        logang@...tatee.com, viro@...iv.linux.org.uk, willy@...radead.org,
        Marc Hartmayer <mhartmay@...ux.ibm.com>
Subject: Re: [PATCH v14 08/17] splice: Do splice read from a file without using ITER_PIPE

Does the attached fix the problem for you?  The data being written into the
pipe needs to be limited to the size of the file.

David

diff --git a/mm/filemap.c b/mm/filemap.c
index c01bbcb9fa92..6362ac697a70 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2948,7 +2948,8 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
 			if (writably_mapped)
 				flush_dcache_folio(folio);
 
-			n = splice_folio_into_pipe(pipe, folio, *ppos, len);
+			n = min_t(loff_t, len, isize - *ppos);
+			n = splice_folio_into_pipe(pipe, folio, *ppos, n);
 			if (!n)
 				goto out;
 			len -= n;