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nfsd: don't replace page in rq_pages if it's a continuation of last page
The splice read calls nfsd_splice_actor to put the pages containing file data into the svc_rqst->rq_pages array. It's possible however to get a splice result that only has a partial page at the end, if (e.g.) the filesystem hands back a short read that doesn't cover the whole page. nfsd_splice_actor will plop the partial page into its rq_pages array and return. Then later, when nfsd_splice_actor is called again, the remainder of the page may end up being filled out. At this point, nfsd_splice_actor will put the page into the array _again_ corrupting the reply. If this is done enough times, rq_next_page will overrun the array and corrupt the trailing fields -- the rq_respages and rq_next_page pointers themselves. If we've already added the page to the array in the last pass, don't add it to the array a second time when dealing with a splice continuation. This was originally handled properly in nfsd_splice_actor, but commit91e23b1c39
("NFSD: Clean up nfsd_splice_actor()") removed the check for it. Fixes:91e23b1c39
("NFSD: Clean up nfsd_splice_actor()") Cc: Al Viro <viro@zeniv.linux.org.uk> Reported-by: Dario Lesca <d.lesca@solinos.it> Tested-by: David Critch <dcritch@redhat.com> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2150630 Signed-off-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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@ -941,8 +941,15 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
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struct page *last_page;
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last_page = page + (offset + sd->len - 1) / PAGE_SIZE;
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for (page += offset / PAGE_SIZE; page <= last_page; page++)
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for (page += offset / PAGE_SIZE; page <= last_page; page++) {
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/*
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* Skip page replacement when extending the contents
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* of the current page.
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*/
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if (page == *(rqstp->rq_next_page - 1))
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continue;
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svc_rqst_replace_page(rqstp, page);
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}
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if (rqstp->rq_res.page_len == 0) // first call
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rqstp->rq_res.page_base = offset % PAGE_SIZE;
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rqstp->rq_res.page_len += sd->len;
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