FAILED: patch "[PATCH] fpga: dfl-afu: validate DMA mapping length in" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x fc3b071a7c8dc0f5d56defddf6e6fd5aaa3e1e27
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026071620-drained-crate-54fa@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From fc3b071a7c8dc0f5d56defddf6e6fd5aaa3e1e27 Mon Sep 17 00:00:00 2001
From: Sebastian Alba Vives <[email protected]>
Date: Mon, 18 May 2026 13:07:41 -0600
Subject: [PATCH] fpga: dfl-afu: validate DMA mapping length in
afu_dma_map_region()

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.

index 3bf8e7338dbe..097a97eeea66 100644
@@ -723,6 +723,9 @@ afu_ioctl_dma_map(struct dfl_feature_dev_data *fdata, 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(fdata, map.user_addr, map.length, &map.iova);
 	if (ret)
 		return ret;

From: Sebastian Alba Vives <[email protected]>

[ 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.

---
 drivers/fpga/dfl-afu-main.c | 3 +++
 1 file changed, 3 insertions(+)

index 7f621e96d3b8d8..dd4107ffa7158c 100644
@@ -720,6 +720,9 @@ 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