accel/qaic: Clean up integer overflow checking in map_user_pages()

The encode_dma() function has some validation on in_trans->size but it
would be more clear to move those checks to find_and_map_user_pages().

The encode_dma() had two checks:

	if (in_trans->addr + in_trans->size < in_trans->addr || !in_trans->size)
		return -EINVAL;

The in_trans->addr variable is the starting address.  The in_trans->size
variable is the total size of the transfer.  The transfer can occur in
parts and the resources->xferred_dma_size tracks how many bytes we have
already transferred.

This patch introduces a new variable "remaining" which represents the
amount we want to transfer (in_trans->size) minus the amount we have
already transferred (resources->xferred_dma_size).

I have modified the check for if in_trans->size is zero to instead check
if in_trans->size is less than resources->xferred_dma_size.  If we have
already transferred more bytes than in_trans->size then there are negative
bytes remaining which doesn't make sense.  If there are zero bytes
remaining to be copied, just return success.

The check in encode_dma() checked that "addr + size" could not overflow
and barring a driver bug that should work, but it's easier to check if
we do this in parts.  First check that "in_trans->addr +
resources->xferred_dma_size" is safe.  Then check that "xfer_start_addr +
remaining" is safe.

My final concern was that we are dealing with u64 values but on 32bit
systems the kmalloc() function will truncate the sizes to 32 bits.  So
I calculated "total = in_trans->size + offset_in_page(xfer_start_addr);"
and returned -EINVAL if it were >= SIZE_MAX.  This will not affect 64bit
systems.

Fixes: 129776ac2e38 ("accel/qaic: Add control path")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Carl Vanderlip <quic_carlv@quicinc.com>
Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Link: https://patchwork.freedesktop.org/patch/msgid/24d3348b-25ac-4c1b-b171-9dae7c43e4e0@moroto.mountain

diff --git a/drivers/accel/qaic/qaic_control.c b/drivers/accel/qaic/qaic_control.c
index cfbc92d..388abd4 100644 (file)
--- a/drivers/accel/qaic/qaic_control.c
+++ b/drivers/accel/qaic/qaic_control.c
@@ -392,18 +392,31 @@ static int find_and_map_user_pages(struct qaic_device *qdev,
                                   struct qaic_manage_trans_dma_xfer *in_trans,
                                   struct ioctl_resources *resources, struct dma_xfer *xfer)
 {
+       u64 xfer_start_addr, remaining, end, total;
        unsigned long need_pages;
        struct page **page_list;
        unsigned long nr_pages;
        struct sg_table *sgt;
-       u64 xfer_start_addr;
        int ret;
        int i;
 
-       xfer_start_addr = in_trans->addr + resources->xferred_dma_size;
+       if (check_add_overflow(in_trans->addr, resources->xferred_dma_size, &xfer_start_addr))
+               return -EINVAL;
 
-       need_pages = DIV_ROUND_UP(in_trans->size + offset_in_page(xfer_start_addr) -
-                                 resources->xferred_dma_size, PAGE_SIZE);
+       if (in_trans->size < resources->xferred_dma_size)
+               return -EINVAL;
+       remaining = in_trans->size - resources->xferred_dma_size;
+       if (remaining == 0)
+               return 0;
+
+       if (check_add_overflow(xfer_start_addr, remaining, &end))
+               return -EINVAL;
+
+       total = remaining + offset_in_page(xfer_start_addr);
+       if (total >= SIZE_MAX)
+               return -EINVAL;
+
+       need_pages = DIV_ROUND_UP(total, PAGE_SIZE);
 
        nr_pages = need_pages;
 
@@ -435,7 +448,7 @@ static int find_and_map_user_pages(struct qaic_device *qdev,
 
        ret = sg_alloc_table_from_pages(sgt, page_list, nr_pages,
                                        offset_in_page(xfer_start_addr),
-                                       in_trans->size - resources->xferred_dma_size, GFP_KERNEL);
+                                       remaining, GFP_KERNEL);
        if (ret) {
                ret = -ENOMEM;
                goto free_sgt;
@@ -566,9 +579,6 @@ static int encode_dma(struct qaic_device *qdev, void *trans, struct wrapper_list
            QAIC_MANAGE_EXT_MSG_LENGTH)
                return -ENOMEM;
 
-       if (in_trans->addr + in_trans->size < in_trans->addr || !in_trans->size)
-               return -EINVAL;
-
        xfer = kmalloc(sizeof(*xfer), GFP_KERNEL);
        if (!xfer)
                return -ENOMEM;