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mm: fix struct page layout on 32-bit systems 

commit 9ddb3c14afba8bc5950ed297f02d4ae05ff35cd1 upstream.

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: c25fff7171 ("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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2021-05-14 17:27:24 -07:00 committed by Greg Kroah-Hartman
parent 187598fd82
commit ecdf893c5a
3 changed files with 16 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/mm_types.h
View File

@ -95,10 +95,10 @@ 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 {

12
include/net/page_pool.h
View File

@ -185,7 +185,17 @@ static inline void page_pool_release_page(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] << 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)

6
net/core/page_pool.c
View File

@ -157,7 +157,7 @@ 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);
skip_dma_map:
/* Track how many pages are held 'in-flight' */
@ -216,12 +216,12 @@ static void __page_pool_clean_page(struct page_pool *pool,
if (!(pool->p.flags & PP_FLAG_DMA_MAP))
goto skip_dma_unmap;
dma = page->dma_addr;
dma = page_pool_get_dma_addr(page);
/* DMA unmap */
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.