From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: brouer@redhat.com
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,
ilias.apalodimas@linaro.org, mcroce@linux.microsoft.com,
grygorii.strashko@ti.com, arnd@kernel.org, hch@lst.de,
linux-snps-arc@lists.infradead.org, mhocko@kernel.org,
mgorman@suse.de
Subject: [PATCH 1/2] mm: Fix struct page layout on 32-bit systems
Date: Sat, 17 Apr 2021 00:07:23 +0100 [thread overview]
Message-ID: <20210416230724.2519198-2-willy@infradead.org> (raw)
In-Reply-To: <20210416230724.2519198-1-willy@infradead.org>
32-bit architectures which expect 8-byte alignment for 8-byte integers
and need 64-bit DMA addresses (arc, 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, and also fixes a
potential problem where (on a big endian platform), the bit used to denote
PageTail could inadvertently get set, and a racing get_user_pages_fast()
could dereference a bogus compound_head().
Fixes: c25fff7171be ("mm: add dma_addr_t to struct page")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.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(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 6613b26a8894..5aacc1c10a45 100644
--- a/include/linux/mm_types.h
+++ b/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 {
diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index b5b195305346..db7c7020746a 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -198,7 +198,17 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
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] << 32;
+ 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] = addr >> 32;
}
static inline bool is_page_pool_compiled_in(void)
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index ad8b0707af04..f014fd8c19a6 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -174,8 +174,10 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool,
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);
}
@@ -226,7 +228,7 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
put_page(page);
return NULL;
}
- 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);
@@ -294,13 +296,13 @@ void page_pool_release_page(struct page_pool *pool, struct page *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.
--
2.30.2
next prev parent reply other threads:[~2021-04-16 23:07 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-16 23:07 [PATCH 0/2] Change struct page layout for page_pool Matthew Wilcox (Oracle)
2021-04-16 23:07 ` Matthew Wilcox (Oracle) [this message]
2021-04-17 1:08 ` [PATCH 1/2] mm: Fix struct page layout on 32-bit systems kernel test robot
2021-04-17 2:45 ` Matthew Wilcox
2021-04-17 18:32 ` Ilias Apalodimas
2021-04-17 20:22 ` Matthew Wilcox
2021-04-18 11:21 ` Ilias Apalodimas
2021-04-17 21:18 ` David Laight
2021-04-17 22:45 ` Matthew Wilcox
2021-04-20 2:48 ` Vineet Gupta
2021-04-20 3:10 ` Matthew Wilcox
2021-04-20 7:07 ` Arnd Bergmann
2021-04-20 21:14 ` Vineet Gupta
2021-04-20 21:20 ` Arnd Bergmann
2021-04-21 5:50 ` hch
2021-04-21 8:43 ` David Laight
2021-04-21 8:58 ` Arnd Bergmann
2021-04-20 7:39 ` Geert Uytterhoeven
2021-04-20 8:39 ` David Laight
2021-04-20 11:32 ` Matthew Wilcox
2021-04-17 7:34 ` Jesper Dangaard Brouer
2021-04-20 7:21 ` Rasmus Villemoes
2021-04-16 23:07 ` [PATCH 2/2] mm: Indicate pfmemalloc pages in compound_head Matthew Wilcox (Oracle)
2021-04-17 21:13 ` David Laight
2021-04-17 21:28 ` Matthew Wilcox
2021-04-20 4:03 ` [PATCH 0/2] Change struct page layout for page_pool Michael Ellerman
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