linux-kernel - [PATCH] dma: fix error handling on out of memory

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Date:	Mon, 11 Oct 2010 11:44:17 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Dan Williams <dan.j.williams@...el.com>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org,
	Maciej Sosnowski <maciej.sosnowski@...el.com>,
	"David S. Miller" <davem@...emloft.net>
Cc:	stable@...nel.org
Subject: [PATCH] dma: fix error handling on out of memory

get_user_pages might return less pages than requested. If this happens
for the first iovec in dma_pin_iovec_pages, then nr_iovecs is 0 and so
dma_unpin_iovec_pages will not unpin any pages, leaking pinned memory.
A similar off by one would trigger for any of the following entries.

Fix by updating nr_iovecs and nr_pages in this case.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---

Error handling in dma_pin_iovec_pages still looks wrong to me.  Am I
missing something?  The following patch against 2.6.36-rc7 was under
some very light testing by me.

Thanks,

 drivers/dma/iovlock.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/drivers/dma/iovlock.c b/drivers/dma/iovlock.c
index bb48a57..21ed8f3 100644
--- a/drivers/dma/iovlock.c
+++ b/drivers/dma/iovlock.c
@@ -107,10 +107,16 @@ struct dma_pinned_list *dma_pin_iovec_pages(struct iovec *iov, size_t len)
 			NULL);
 		up_read(&current->mm->mmap_sem);
 
-		if (ret != page_list->nr_pages)
+		if (unlikely(ret < 0))
 			goto unpin;
 
 		local_list->nr_iovecs = i + 1;
+
+		if (unlikely(ret != page_list->nr_pages)) {
+			page_list->nr_pages = ret;
+			goto unpin;
+		}
+
 	}
 
 	return local_list;
-- 
MST
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