From: Tvrtko Ursulin <tursulin@ursulin.net>
To: Intel-gfx@lists.freedesktop.org
Cc: Ben Widawsky <benjamin.widawsky@intel.com>,
Jason Ekstrand <jason@jlekstrand.net>,
Tvrtko Ursulin <tvrtko.ursulin@intel.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
linux-kernel@vger.kernel.org,
Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: [PATCH 2/4] lib/scatterlist: Avoid potential scatterlist entry overflow
Date: Thu, 27 Jul 2017 10:05:02 +0100 [thread overview]
Message-ID: <20170727090504.15812-3-tvrtko.ursulin@linux.intel.com> (raw)
In-Reply-To: <20170727090504.15812-1-tvrtko.ursulin@linux.intel.com>
From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Since the scatterlist length field is an unsigned int, make
sure that sg_alloc_table_from_pages does not overflow it while
coallescing pages to a single entry.
v2: Drop reference to future use. Use UINT_MAX.
v3: max_segment must be page aligned.
v4: Do not rely on compiler to optimise out the rounddown.
(Joonas Lahtinen)
v5: Simplified loops and use post-increments rather than
pre-increments. Use PAGE_MASK and fix comment typo.
(Andy Shevchenko)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> (v2)
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
---
include/linux/scatterlist.h | 6 ++++++
lib/scatterlist.c | 31 ++++++++++++++++++++-----------
2 files changed, 26 insertions(+), 11 deletions(-)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 205aefb4ed93..6dd2ddbc6230 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -21,6 +21,12 @@ struct scatterlist {
};
/*
+ * Since the above length field is an unsigned int, below we define the maximum
+ * length in bytes that can be stored in one scatterlist entry.
+ */
+#define SCATTERLIST_MAX_SEGMENT (UINT_MAX & PAGE_MASK)
+
+/*
* These macros should be used after a dma_map_sg call has been done
* to get bus addresses of each of the SG entries and their lengths.
* You should only work with the number of sg entries dma_map_sg
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index dee0c5004e2f..7b2e74da2c44 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -394,17 +394,22 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
unsigned int offset, unsigned long size,
gfp_t gfp_mask)
{
- unsigned int chunks;
- unsigned int i;
- unsigned int cur_page;
+ const unsigned int max_segment = SCATTERLIST_MAX_SEGMENT;
+ unsigned int chunks, cur_page, seg_len, i;
int ret;
struct scatterlist *s;
/* compute number of contiguous chunks */
chunks = 1;
- for (i = 1; i < n_pages; ++i)
- if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
- ++chunks;
+ seg_len = 0;
+ for (i = 1; i < n_pages; i++) {
+ seg_len += PAGE_SIZE;
+ if (seg_len >= max_segment ||
+ page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) {
+ chunks++;
+ seg_len = 0;
+ }
+ }
ret = sg_alloc_table(sgt, chunks, gfp_mask);
if (unlikely(ret))
@@ -413,17 +418,21 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
/* merging chunks and putting them into the scatterlist */
cur_page = 0;
for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
- unsigned long chunk_size;
- unsigned int j;
+ unsigned int j, chunk_size;
/* look for the end of the current chunk */
- for (j = cur_page + 1; j < n_pages; ++j)
- if (page_to_pfn(pages[j]) !=
+ seg_len = 0;
+ for (j = cur_page + 1; j < n_pages; j++) {
+ seg_len += PAGE_SIZE;
+ if (seg_len >= max_segment ||
+ page_to_pfn(pages[j]) !=
page_to_pfn(pages[j - 1]) + 1)
break;
+ }
chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
- sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
+ sg_set_page(s, pages[cur_page],
+ min_t(unsigned long, size, chunk_size), offset);
size -= chunk_size;
offset = 0;
cur_page = j;
--
2.9.4
next prev parent reply other threads:[~2017-07-27 9:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20170727090504.15812-1-tvrtko.ursulin@linux.intel.com>
2017-07-27 9:05 ` [PATCH 1/4] lib/scatterlist: Fix offset type in sg_alloc_table_from_pages Tvrtko Ursulin
2017-07-27 9:05 ` Tvrtko Ursulin [this message]
2017-07-28 10:53 ` [Intel-gfx] [PATCH 2/4] lib/scatterlist: Avoid potential scatterlist entry overflow Chris Wilson
2017-07-27 9:05 ` [PATCH 3/4] lib/scatterlist: Introduce and export __sg_alloc_table_from_pages Tvrtko Ursulin
2017-07-28 11:07 ` Chris Wilson
2017-08-02 13:06 ` [Intel-gfx] " Tvrtko Ursulin
2017-08-02 23:01 ` Andrew Morton
2017-08-03 9:21 ` Tvrtko Ursulin
2017-07-27 9:05 ` [PATCH 4/4] drm/i915: Use __sg_alloc_table_from_pages for userptr allocations Tvrtko Ursulin
2017-07-28 11:06 ` Chris Wilson
2017-05-04 15:54 [PATCH 1/4] lib/scatterlist: Fix offset type in sg_alloc_table_from_pages Tvrtko Ursulin
2017-05-04 15:54 ` [PATCH 2/4] lib/scatterlist: Avoid potential scatterlist entry overflow Tvrtko Ursulin
-- strict thread matches above, loose matches on Subject: below --
2017-01-16 14:12 [PATCH 1/4] lib/scatterlist: Fix offset type in sg_alloc_table_from_pages Tvrtko Ursulin
2017-01-16 14:12 ` [PATCH 2/4] lib/scatterlist: Avoid potential scatterlist entry overflow Tvrtko Ursulin
2017-01-11 9:00 [PATCH 1/4] lib/scatterlist: Fix offset type in sg_alloc_table_from_pages Tvrtko Ursulin
2017-01-11 9:00 ` [PATCH 2/4] lib/scatterlist: Avoid potential scatterlist entry overflow Tvrtko Ursulin
2016-11-11 8:50 [PATCH 0/4] Compact userptr object backing store allocation Tvrtko Ursulin
2016-11-11 8:50 ` [PATCH 2/4] lib/scatterlist: Avoid potential scatterlist entry overflow Tvrtko Ursulin
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