From: Eric Sandeen <sandeen@sandeen.net> To: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Christoph@sandeen.net, Hellwig@sandeen.net, <hch@lst.de> Subject: [PATCH 2/3] iomap: don't search past page end in iomap_is_partially_uptodate Date: Thu, 13 Dec 2018 16:25:28 -0600 [thread overview] Message-ID: <1544739929-21651-3-git-send-email-sandeen@sandeen.net> (raw) In-Reply-To: <1544739929-21651-1-git-send-email-sandeen@sandeen.net> From: Eric Sandeen <sandeen@redhat.com> 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 <zlang@redhat.com> Signed-off-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Eric Sandeen <sandeen@sandeen.net> --- fs/iomap.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/iomap.c b/fs/iomap.c index d6bc98a..ce837d9 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -492,16 +492,29 @@ struct iomap_readpage_ctx { } 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)) -- 1.8.3.1
WARNING: multiple messages have this Message-ID (diff)
From: Eric Sandeen <sandeen@sandeen.net> To: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Christoph@sandeen.net, Hellwig@sandeen.net, hch@lst.de Subject: [PATCH 2/3] iomap: don't search past page end in iomap_is_partially_uptodate Date: Thu, 13 Dec 2018 16:25:28 -0600 [thread overview] Message-ID: <1544739929-21651-3-git-send-email-sandeen@sandeen.net> (raw) In-Reply-To: <1544739929-21651-1-git-send-email-sandeen@sandeen.net> From: Eric Sandeen <sandeen@redhat.com> 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 <zlang@redhat.com> Signed-off-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Eric Sandeen <sandeen@sandeen.net> --- fs/iomap.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/iomap.c b/fs/iomap.c index d6bc98a..ce837d9 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -492,16 +492,29 @@ struct iomap_readpage_ctx { } 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)) -- 1.8.3.1
next prev parent reply other threads:[~2018-12-13 22:25 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-12-13 22:25 [PATCH 0/3] iomap: 1 cleanup, 1 fix, 1 optimization Eric Sandeen 2018-12-13 22:25 ` Eric Sandeen 2018-12-13 22:25 ` [PATCH 1/3] iomap: use SECTOR_SIZE instead of 512 in iomap_page Eric Sandeen 2018-12-13 22:25 ` Eric Sandeen 2018-12-15 10:51 ` Christoph Hellwig 2018-12-17 23:45 ` Eric Sandeen 2018-12-18 18:06 ` Christoph Hellwig 2018-12-18 18:19 ` Darrick J. Wong 2018-12-18 18:20 ` Eric Sandeen 2018-12-13 22:25 ` Eric Sandeen [this message] 2018-12-13 22:25 ` [PATCH 2/3] iomap: don't search past page end in iomap_is_partially_uptodate Eric Sandeen 2018-12-14 2:57 ` Dave Chinner 2018-12-14 13:48 ` Eric Sandeen 2018-12-14 22:14 ` [PATCH 2/3 V2] mm: don't search past page end in is_partially_uptodate Eric Sandeen 2018-12-15 10:49 ` Christoph Hellwig 2018-12-13 22:25 ` [PATCH 3/3] iomap: optimize iomap_is_partially_uptodate for full page range Eric Sandeen 2018-12-13 22:25 ` Eric Sandeen 2018-12-14 3:05 ` Dave Chinner 2018-12-14 14:10 ` Eric Sandeen 2018-12-17 23:21 ` Dave Chinner 2018-12-13 22:27 ` [PATCH 0/3] iomap: 1 cleanup, 1 fix, 1 optimization Eric Sandeen
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