[PATCH 5.10.y] fpga: dfl-afu: validate DMA mapping length in afu_dma_map_region()

[Sasha Levin <sashal@kernel.org>]

From: Sebastian Alba Vives <sebasjosue84@gmail.com>

[ Upstream commit fc3b071a7c8dc0f5d56defddf6e6fd5aaa3e1e27 ]

afu_ioctl_dma_map() accepts a 64-bit length from userspace via
DFL_FPGA_PORT_DMA_MAP ioctl without an upper bound check. The value
is passed to afu_dma_pin_pages() where npages is derived as
length >> PAGE_SHIFT and passed to pin_user_pages_fast() which takes
int nr_pages, causing implicit truncation if length is very large.

Validate map.length at the ioctl entry point before calling
afu_dma_map_region(), rejecting values whose page count exceeds
INT_MAX.

Fixes: fa8dda1edef9 ("fpga: dfl: afu: add DFL_FPGA_PORT_DMA_MAP/UNMAP ioctls support")
Cc: stable@vger.kernel.org
Signed-off-by: Sebastian Alba Vives <sebasjosue84@gmail.com>
Reviewed-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20260518190742.61426-3-sebasjosue84@gmail.com
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/fpga/dfl-afu-main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/fpga/dfl-afu-main.c b/drivers/fpga/dfl-afu-main.c
index 753cda4b256838..b85e0624ab8f95 100644
--- a/drivers/fpga/dfl-afu-main.c
+++ b/drivers/fpga/dfl-afu-main.c
@@ -707,6 +707,9 @@ afu_ioctl_dma_map(struct dfl_feature_platform_data *pdata, void __user *arg)
 	if (map.argsz < minsz || map.flags)
 		return -EINVAL;
 
+	if (map.length >> PAGE_SHIFT > (u64)INT_MAX)
+		return -EINVAL;
+
 	ret = afu_dma_map_region(pdata, map.user_addr, map.length, &map.iova);
 	if (ret)
 		return ret;
-- 
2.53.0