From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Eric Sandeen , Eric Sandeen , "Darrick J . Wong" , Sasha Levin , linux-fsdevel@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 92/97] iomap: don't search past page end in iomap_is_partially_uptodate Date: Tue, 8 Jan 2019 14:29:41 -0500 Message-Id: <20190108192949.122407-92-sashal@kernel.org> In-Reply-To: <20190108192949.122407-1-sashal@kernel.org> References: <20190108192949.122407-1-sashal@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit List-ID: From: Eric Sandeen [ Upstream commit 3cc31fa65d85610574c0f6a474e89f4c419923d5 ] iomap_is_partially_uptodate() is intended to check wither blocks within the selected range of a not-uptodate page are uptodate; if the range we care about is up to date, it's an optimization. However, the iomap implementation continues to check all blocks up to from+count, which is beyond the page, and can even be well beyond the iop->uptodate bitmap. I think the worst that will happen is that we may eventually find a zero bit and return "not partially uptodate" when it would have otherwise returned true, and skip the optimization. Still, it's clearly an invalid memory access that must be fixed. So: fix this by limiting the search to within the page as is done in the non-iomap variant, block_is_partially_uptodate(). Zorro noticed thiswhen KASAN went off for 512 byte blocks on a 64k page system: BUG: KASAN: slab-out-of-bounds in iomap_is_partially_uptodate+0x1a0/0x1e0 Read of size 8 at addr ffff800120c3a318 by task fsstress/22337 Reported-by: Zorro Lang Signed-off-by: Eric Sandeen Signed-off-by: Eric Sandeen Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Signed-off-by: Sasha Levin --- fs/iomap.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/iomap.c b/fs/iomap.c index ec15cf2ec696..e57fb1e534c5 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -488,16 +488,29 @@ iomap_readpages(struct address_space *mapping, struct list_head *pages, } EXPORT_SYMBOL_GPL(iomap_readpages); +/* + * iomap_is_partially_uptodate checks whether blocks within a page are + * uptodate or not. + * + * Returns true if all blocks which correspond to a file portion + * we want to read within the page are uptodate. + */ int iomap_is_partially_uptodate(struct page *page, unsigned long from, unsigned long count) { struct iomap_page *iop = to_iomap_page(page); struct inode *inode = page->mapping->host; - unsigned first = from >> inode->i_blkbits; - unsigned last = (from + count - 1) >> inode->i_blkbits; + unsigned len, first, last; unsigned i; + /* Limit range to one page */ + len = min_t(unsigned, PAGE_SIZE - from, count); + + /* First and last blocks in range within page */ + first = from >> inode->i_blkbits; + last = (from + len - 1) >> inode->i_blkbits; + if (iop) { for (i = first; i <= last; i++) if (!test_bit(i, iop->uptodate)) -- 2.19.1