FAILED: patch "[PATCH] swiotlb: use the adjusted address for the highmem page lookup" failed to apply to 6.12-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.12-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 <stable@vger.kernel.org>.

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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x b7d7914a9ae3097e63d113007e4fb44d33d515b1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026092244-diocese-pointing-0bdd@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From b7d7914a9ae3097e63d113007e4fb44d33d515b1 Mon Sep 17 00:00:00 2001
From: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Date: Sat, 5 Sep 2026 17:42:10 +0900
Subject: [PATCH] swiotlb: use the adjusted address for the highmem page lookup

swiotlb_bounce() reads the page frame number from the slot's recorded
orig_addr, then advances orig_addr by tlb_offset to reach the address
the caller asked about. The highmem branch mixes the two: the offset
within the page comes from the adjusted address, the page from the value
before it.

Once the adjustment crosses a page boundary the pair no longer describes
one location, and the whole copy lands one page below the intended one
for a positive tlb_offset, one above for a negative one. DMA_FROM_DEVICE
writes the device data over the wrong page and leaves the intended one
stale, DMA_TO_DEVICE feeds the device from a page the mapping may not
cover. Partial syncs through dma_sync_single_range_for_*() are what make
tlb_offset non-zero.

The branch test is picked the same way, so a slot recorded in lowmem can
be adjusted into highmem and the lowmem path then hands a highmem
address to phys_to_virt().

Take both from orig_addr once it is final and keep pfn in the branch
that uses it. PhysHighMem() asks the question straight from the address,
as dma-debug already does.

Fixes: 5f89468e2f06 ("swiotlb: manipulate orig_addr when tlb_addr has offset")
Cc: stable@vger.kernel.org
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20260905084210.148255-1-donggeunyoo.kernel@gmail.com
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index ded7016a46a7..aa2f1c4588b9 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1019,7 +1019,6 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
 	int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT;
 	phys_addr_t orig_addr = mem->slots[index].orig_addr;
 	size_t alloc_size = mem->slots[index].alloc_size;
-	unsigned long pfn = PFN_DOWN(orig_addr);
 	unsigned char *vaddr = mem->vaddr + tlb_addr - mem->start;
 	int tlb_offset;
 
@@ -1052,7 +1051,8 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
 		size = alloc_size;
 	}
 
-	if (PageHighMem(pfn_to_page(pfn))) {
+	if (PhysHighMem(orig_addr)) {
+		unsigned long pfn = PFN_DOWN(orig_addr);
 		unsigned int offset = orig_addr & ~PAGE_MASK;
 		struct page *page;
 		unsigned int sz = 0;