From 6db3ac3c4bc552837d232ec794559a2fae2815a0 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 16 Mar 2017 16:27:44 +0000 Subject: afs: Handle better the server returning excess or short data When an AFS server is given an FS.FetchData{,64} request to read data from a file, it is permitted by the protocol to return more or less than was requested. kafs currently relies on the latter behaviour in readpage{,s} to handle a partial page at the end of the file (we just ask for a whole page and clear space beyond the short read). However, we don't handle all cases. Add: (1) Handle excess data by discarding it rather than aborting. Note that we use a common static buffer to discard into so that the decryption algorithm advances the PCBC state. (2) Handle a short read that affects more than just the last page. Note that if a read comes up unexpectedly short of long, it's possible that the server's copy of the file changed - in which case the data version number will have been incremented and the callback will have been broken - in which case all the pages currently attached to the inode will be zapped anyway at some point. Signed-off-by: David Howells --- fs/afs/file.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'fs/afs/file.c') diff --git a/fs/afs/file.c b/fs/afs/file.c index ba7b71f..a38e1c3 100644 --- a/fs/afs/file.c +++ b/fs/afs/file.c @@ -184,10 +184,13 @@ int afs_page_filler(void *data, struct page *page) if (!req) goto enomem; + /* We request a full page. If the page is a partial one at the + * end of the file, the server will return a short read and the + * unmarshalling code will clear the unfilled space. + */ atomic_set(&req->usage, 1); req->pos = (loff_t)page->index << PAGE_SHIFT; - req->len = min_t(size_t, i_size_read(inode) - req->pos, - PAGE_SIZE); + req->len = PAGE_SIZE; req->nr_pages = 1; req->pages[0] = page; get_page(page); -- cgit v1.1