linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, brouer@redhat.com,
	ilias.apalodimas@linaro.org, linux-mm@kvack.org,
	mcroce@linux.microsoft.com, mm-commits@vger.kernel.org,
	stable@vger.kernel.org, torvalds@linux-foundation.org,
	vbabka@suse.cz, willy@infradead.org
Subject: [patch 08/13] mm: fix struct page layout on 32-bit systems
Date: Fri, 14 May 2021 17:27:24 -0700	[thread overview]
Message-ID: <20210515002724.4C8uJfcjY%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210514172634.9018621171d5334ceee97e95@linux-foundation.org>

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: mm: fix struct page layout on 32-bit systems

32-bit architectures which expect 8-byte alignment for 8-byte integers and
need 64-bit DMA addresses (arm, mips, ppc) had their struct page
inadvertently expanded in 2019.  When the dma_addr_t was added, it forced
the alignment of the union to 8 bytes, which inserted a 4 byte gap between
'flags' and the union.

Fix this by storing the dma_addr_t in one or two adjacent unsigned longs.
This restores the alignment to that of an unsigned long.  We always
store the low bits in the first word to prevent the PageTail bit from
being inadvertently set on a big endian platform.  If that happened,
get_user_pages_fast() racing against a page which was freed and
reallocated to the page_pool could dereference a bogus compound_head(),
which would be hard to trace back to this cause.

Link: https://lkml.kernel.org/r/20210510153211.1504886-1-willy@infradead.org
Fixes: c25fff7171be ("mm: add dma_addr_t to struct page")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Matteo Croce <mcroce@linux.microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm_types.h |    4 ++--
 include/net/page_pool.h  |   12 +++++++++++-
 net/core/page_pool.c     |   12 +++++++-----
 3 files changed, 20 insertions(+), 8 deletions(-)

--- a/include/linux/mm_types.h~mm-fix-struct-page-layout-on-32-bit-systems
+++ a/include/linux/mm_types.h
@@ -97,10 +97,10 @@ struct page {
 		};
 		struct {	/* page_pool used by netstack */
 			/**
-			 * @dma_addr: might require a 64-bit value even on
+			 * @dma_addr: might require a 64-bit value on
 			 * 32-bit architectures.
 			 */
-			dma_addr_t dma_addr;
+			unsigned long dma_addr[2];
 		};
 		struct {	/* slab, slob and slub */
 			union {
--- a/include/net/page_pool.h~mm-fix-struct-page-layout-on-32-bit-systems
+++ a/include/net/page_pool.h
@@ -198,7 +198,17 @@ static inline void page_pool_recycle_dir
 
 static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
 {
-	return page->dma_addr;
+	dma_addr_t ret = page->dma_addr[0];
+	if (sizeof(dma_addr_t) > sizeof(unsigned long))
+		ret |= (dma_addr_t)page->dma_addr[1] << 16 << 16;
+	return ret;
+}
+
+static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
+{
+	page->dma_addr[0] = addr;
+	if (sizeof(dma_addr_t) > sizeof(unsigned long))
+		page->dma_addr[1] = upper_32_bits(addr);
 }
 
 static inline bool is_page_pool_compiled_in(void)
--- a/net/core/page_pool.c~mm-fix-struct-page-layout-on-32-bit-systems
+++ a/net/core/page_pool.c
@@ -174,8 +174,10 @@ static void page_pool_dma_sync_for_devic
 					  struct page *page,
 					  unsigned int dma_sync_size)
 {
+	dma_addr_t dma_addr = page_pool_get_dma_addr(page);
+
 	dma_sync_size = min(dma_sync_size, pool->p.max_len);
-	dma_sync_single_range_for_device(pool->p.dev, page->dma_addr,
+	dma_sync_single_range_for_device(pool->p.dev, dma_addr,
 					 pool->p.offset, dma_sync_size,
 					 pool->p.dma_dir);
 }
@@ -195,7 +197,7 @@ static bool page_pool_dma_map(struct pag
 	if (dma_mapping_error(pool->p.dev, dma))
 		return false;
 
-	page->dma_addr = dma;
+	page_pool_set_dma_addr(page, dma);
 
 	if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
 		page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
@@ -331,13 +333,13 @@ void page_pool_release_page(struct page_
 		 */
 		goto skip_dma_unmap;
 
-	dma = page->dma_addr;
+	dma = page_pool_get_dma_addr(page);
 
-	/* When page is unmapped, it cannot be returned our pool */
+	/* When page is unmapped, it cannot be returned to our pool */
 	dma_unmap_page_attrs(pool->p.dev, dma,
 			     PAGE_SIZE << pool->p.order, pool->p.dma_dir,
 			     DMA_ATTR_SKIP_CPU_SYNC);
-	page->dma_addr = 0;
+	page_pool_set_dma_addr(page, 0);
 skip_dma_unmap:
 	/* This may be the last page returned, releasing the pool, so
 	 * it is not safe to reference pool afterwards.
_


  parent reply	other threads:[~2021-05-15  0:27 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-15  0:26 incoming Andrew Morton
2021-05-15  0:27 ` [patch 01/13] mm/hugetlb: fix F_SEAL_FUTURE_WRITE Andrew Morton
2021-05-15  0:27 ` [patch 02/13] mm/hugetlb: fix cow where page writtable in child Andrew Morton
2021-05-15  0:27 ` [patch 03/13] mm, slub: move slub_debug static key enabling outside slab_mutex Andrew Morton
2021-05-15  0:27 ` [patch 04/13] kernel/resource: fix return code check in __request_free_mem_region Andrew Morton
2021-05-15  0:27 ` [patch 05/13] squashfs: fix divide error in calculate_skip() Andrew Morton
2021-05-15  0:27 ` [patch 06/13] userfaultfd: release page in error path to avoid BUG_ON Andrew Morton
2021-05-15  0:27 ` [patch 07/13] ksm: revert "use GET_KSM_PAGE_NOLOCK to get ksm page in remove_rmap_item_from_tree()" Andrew Morton
2021-05-15  0:27 ` Andrew Morton [this message]
2021-05-15  0:27 ` [patch 09/13] kasan: fix unit tests with CONFIG_UBSAN_LOCAL_BOUNDS enabled Andrew Morton
2021-05-15  0:27 ` [patch 10/13] mm/filemap: fix readahead return types Andrew Morton
2021-05-15  0:27 ` [patch 11/13] hfsplus: prevent corruption in shrinking truncate Andrew Morton
2021-05-15  0:27 ` [patch 12/13] docs: admin-guide: update description for kernel.modprobe sysctl Andrew Morton
2021-05-15  0:27 ` [patch 13/13] mm/ioremap: fix iomap_max_page_shift Andrew Morton

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210515002724.4C8uJfcjY%akpm@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=brouer@redhat.com \
    --cc=ilias.apalodimas@linaro.org \
    --cc=linux-mm@kvack.org \
    --cc=mcroce@linux.microsoft.com \
    --cc=mm-commits@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    --cc=torvalds@linux-foundation.org \
    --cc=vbabka@suse.cz \
    --cc=willy@infradead.org \
    --subject='Re: [patch 08/13] mm: fix struct page layout on 32-bit systems' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).