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Subject[PATCH 07/10] udmabuf: rework limits
Date
Create variable for the list length limit.  Serves as documentation,
also allows to make it a module parameter if needed.

Also add a total size limit.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
drivers/dma-buf/udmabuf.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 0cf7e85585..cb99a7886a 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -12,6 +12,9 @@
#include <linux/shmem_fs.h>
#include <linux/udmabuf.h>

+static int list_limit = 1024; /* udmabuf_create_list->count limit */
+static int size_limit_mb = 64; /* total dmabuf size, in megabytes */
+
struct udmabuf {
pgoff_t pagecount;
struct page **pages;
@@ -123,7 +126,7 @@ static long udmabuf_create(struct const udmabuf_create_list *head,
struct file *memfd = NULL;
struct udmabuf *ubuf;
struct dma_buf *buf;
- pgoff_t pgoff, pgcnt, pgidx, pgbuf;
+ pgoff_t pgoff, pgcnt, pgidx, pgbuf, pglimit;
struct page *page;
int seals, ret = -EINVAL;
u32 i, flags;
@@ -132,12 +135,15 @@ static long udmabuf_create(struct const udmabuf_create_list *head,
if (!ubuf)
return -ENOMEM;

+ pglimit = (size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
for (i = 0; i < head->count; i++) {
if (!IS_ALIGNED(list[i].offset, PAGE_SIZE))
goto err_free_ubuf;
if (!IS_ALIGNED(list[i].size, PAGE_SIZE))
goto err_free_ubuf;
ubuf->pagecount += list[i].size >> PAGE_SHIFT;
+ if (ubuf->pagecount > pglimit)
+ goto err_free_ubuf;
}
ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(struct page *),
GFP_KERNEL);
@@ -227,7 +233,7 @@ static long udmabuf_ioctl_create_list(struct file *filp, unsigned long arg)

if (copy_from_user(&head, (void __user *)arg, sizeof(head)))
return -EFAULT;
- if (head.count > 1024)
+ if (head.count > list_limit)
return -EINVAL;
lsize = sizeof(struct udmabuf_create_item) * head.count;
list = memdup_user((void __user *)(arg + sizeof(head)), lsize);
--
2.9.3
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