| Message ID | 20190608164853.10938-3-ming.lei@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: fix page leak by merging to same page | expand |
On Sun, Jun 9, 2019 at 12:50 AM Ming Lei <ming.lei@redhat.com> wrote: > > Different iovec may use one same page, then 'pages' array filled > by iov_iter_get_pages() may get reference of the same page several > times. If some page in 'pages' can be merged to same page in one bvec > by bio_add_page(), bio_release_pages() only drops the page's reference > once. > > This way causes page leak reported by David Gibson. > > This issue can be triggered since 576ed913 ("block: use bio_add_page in > bio_iov_iter_get_pages"). > > Fixes the issue by put the page's ref if it is merged to same page. > > Cc: David Gibson <david@gibson.dropbear.id.au> > Cc: "Darrick J. Wong" <darrick.wong@oracle.com> > Cc: linux-xfs@vger.kernel.org > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: Christoph Hellwig <hch@infradead.org> > Link: https://lkml.org/lkml/2019/4/23/64 > Fixes: 576ed913 ("block: use bio_add_page in bio_iov_iter_get_pages") > Reported-by: David Gibson <david@gibson.dropbear.id.au> > Signed-off-by: Ming Lei <ming.lei@redhat.com> > --- > block/bio.c | 14 ++++++++++++-- > include/linux/bio.h | 1 + > 2 files changed, 13 insertions(+), 2 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index 39e3b931dc3b..5f7b46360c36 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -657,6 +657,10 @@ static inline bool page_is_mergeable(const struct bio_vec *bv, > WARN_ON_ONCE((flags & BVEC_MERGE_TO_SAME_PAGE) && > (len + off) > PAGE_SIZE); > > + if ((flags & BVEC_MERGE_PUT_SAME_PAGE) && > + (flags & BVEC_MERGE_TO_SAME_PAGE)) > + put_page(page); > + > return true; > } > > @@ -924,8 +928,14 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > struct page *page = pages[i]; > > len = min_t(size_t, PAGE_SIZE - offset, left); > - if (WARN_ON_ONCE(bio_add_page(bio, page, len, offset) != len)) > - return -EINVAL; > + > + if (!__bio_try_merge_page(bio, page, len, offset, > + BVEC_MERGE_PUT_SAME_PAGE | > + BVEC_MERGE_TO_SAME_PAGE)) { oops, it is wrong to pass BVEC_MERGE_TO_SAME_PAGE here, which should disable multi-page merge. Please ignore this patchset, and will fix it in V2. Thanks, Ming Lei
diff --git a/block/bio.c b/block/bio.c index 39e3b931dc3b..5f7b46360c36 100644 --- a/block/bio.c +++ b/block/bio.c @@ -657,6 +657,10 @@ static inline bool page_is_mergeable(const struct bio_vec *bv, WARN_ON_ONCE((flags & BVEC_MERGE_TO_SAME_PAGE) && (len + off) > PAGE_SIZE); + if ((flags & BVEC_MERGE_PUT_SAME_PAGE) && + (flags & BVEC_MERGE_TO_SAME_PAGE)) + put_page(page); + return true; } @@ -924,8 +928,14 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) struct page *page = pages[i]; len = min_t(size_t, PAGE_SIZE - offset, left); - if (WARN_ON_ONCE(bio_add_page(bio, page, len, offset) != len)) - return -EINVAL; + + if (!__bio_try_merge_page(bio, page, len, offset, + BVEC_MERGE_PUT_SAME_PAGE | + BVEC_MERGE_TO_SAME_PAGE)) { + if (WARN_ON_ONCE(bio_add_page(bio, page, len, offset) + != len)) + return -EINVAL; + } offset = 0; } diff --git a/include/linux/bio.h b/include/linux/bio.h index 48a95bca1703..dec6cf683d8e 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -422,6 +422,7 @@ void bio_chain(struct bio *, struct bio *); enum bvec_merge_flags { BVEC_MERGE_DEFAULT, BVEC_MERGE_TO_SAME_PAGE = BIT(0), + BVEC_MERGE_PUT_SAME_PAGE = BIT(1), }; extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
Different iovec may use one same page, then 'pages' array filled by iov_iter_get_pages() may get reference of the same page several times. If some page in 'pages' can be merged to same page in one bvec by bio_add_page(), bio_release_pages() only drops the page's reference once. This way causes page leak reported by David Gibson. This issue can be triggered since 576ed913 ("block: use bio_add_page in bio_iov_iter_get_pages"). Fixes the issue by put the page's ref if it is merged to same page. Cc: David Gibson <david@gibson.dropbear.id.au> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: linux-xfs@vger.kernel.org Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Link: https://lkml.org/lkml/2019/4/23/64 Fixes: 576ed913 ("block: use bio_add_page in bio_iov_iter_get_pages") Reported-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Ming Lei <ming.lei@redhat.com> --- block/bio.c | 14 ++++++++++++-- include/linux/bio.h | 1 + 2 files changed, 13 insertions(+), 2 deletions(-)