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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: Christoph Hellwig , Al Viro , Matthew Wilcox cc: dhowells@redhat.com, torvalds@linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Should iov_iter_get_pages*() be EXPORT_SYMBOL_GPL? MIME-Version: 1.0 Content-ID: <1464423.1669210515.1@warthog.procyon.org.uk> Date: Wed, 23 Nov 2022 13:35:15 +0000 Message-ID: <1464424.1669210515@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1750295465837352375?= X-GMAIL-MSGID: =?utf-8?q?1750295465837352375?= I recently posted an intended replacement[1] for iov_iter_get_pages*() which, instead of always just getting a ref on the pages it extracts from the iterator it is given, will pin them or leave them unaltered (but still in the list) as appropriate. However, Christoph objected[2] to my using EXPORT_SYMBOL() with it on the basis that: get_user_pages_fast, pin_user_pages_fast are very intentionally EXPORT_SYMBOL_GPL, which should not be bypassed by an iov_* wrapper. but iov_iter_get_pages*() is EXPORT_SYMBOL(), so it's already possible to bypass this restriction. He has also raised other objections[3]. Should we then convert this to EXPORT_SYMBOL_GPL(), as per the attached patch? Link: https://lore.kernel.org/r/166920902005.1461876.2786264600108839814.stgit@warthog.procyon.org.uk/ [1] Link: https://lore.kernel.org/r/Y3zFzdWnWlEJ8X8/@infradead.org/ [2] Link: https://lore.kernel.org/lkml/20221025154143.GA25128@lst.de/ [3] --- iov_iter: Mark iov_iter_get_pages2*() as EXPORT_SYMBOL_GPL() iov_iter_get_pages2*() should be marked EXPORT_SYMBOL_GPL() as the use get_user_pages_fast()[1]. Reported-by: Christoph Hellwig Signed-off-by: David Howells cc: Al Viro cc: Matthew Wilcox cc: linux-mm@kvack.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/Y3zFzdWnWlEJ8X8/@infradead.org/ [1] --- iov_iter.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 612fc9bf9881..02b02a5fece4 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1502,7 +1502,7 @@ ssize_t iov_iter_get_pages2(struct iov_iter *i, return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start); } -EXPORT_SYMBOL(iov_iter_get_pages2); +EXPORT_SYMBOL_GPL(iov_iter_get_pages2); ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages, size_t maxsize, @@ -1519,7 +1519,7 @@ ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, } return len; } -EXPORT_SYMBOL(iov_iter_get_pages_alloc2); +EXPORT_SYMBOL_GPL(iov_iter_get_pages_alloc2); size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i)