From a90bcb86ae700c12432446c4aa1819e7b8e172ec Mon Sep 17 00:00:00 2001 From: Petar Penkov Date: Tue, 29 Aug 2017 11:20:32 -0700 Subject: [PATCH] iov_iter: fix page_copy_sane for compound pages Issue is that if the data crosses a page boundary inside a compound page, this check will incorrectly trigger a WARN_ON. To fix this, compute the order using the head of the compound page and adjust the offset to be relative to that head. Fixes: 72e809ed81ed ("iov_iter: sanity checks for copy to/from page primitives") Signed-off-by: Petar Penkov CC: Al Viro CC: Eric Dumazet Signed-off-by: Al Viro --- lib/iov_iter.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 52c8dd6d8e82..1c1c06ddc20a 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -687,8 +687,10 @@ EXPORT_SYMBOL(_copy_from_iter_full_nocache); static inline bool page_copy_sane(struct page *page, size_t offset, size_t n) { - size_t v = n + offset; - if (likely(n <= v && v <= (PAGE_SIZE << compound_order(page)))) + struct page *head = compound_head(page); + size_t v = n + offset + page_address(page) - page_address(head); + + if (likely(n <= v && v <= (PAGE_SIZE << compound_order(head)))) return true; WARN_ON(1); return false; -- 2.20.1