This is a note to let you know that I've just added the patch titled
net: ipa: avoid 64-bit modulus
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-ipa-avoid-64-bit-modulus.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8b5ff5ce40741e9917658be1a354270767d7f247
Author: Alex Elder <elder@xxxxxxxxxx>
Date: Mon Mar 22 20:05:05 2021 -0500
net: ipa: avoid 64-bit modulus
[ Upstream commit 437c78f976f5b39fc4b2a1c65903a229f55912dd ]
It is possible for a 32 bit x86 build to use a 64 bit DMA address.
There are two remaining spots where the IPA driver does a modulo
operation to check alignment of a DMA address, and under certain
conditions this can lead to a build error on i386 (at least).
The alignment checks we're doing are for power-of-2 values, and this
means the lower 32 bits of the DMA address can be used. This ensures
both operands to the modulo operator are 32 bits wide.
Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
Acked-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> # build-tested
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Stable-dep-of: cf412ec33325 ("net: ipa: properly limit modem routing table use")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index fe91b72eca36..e46d3622f9eb 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -1251,15 +1251,18 @@ static void gsi_evt_ring_rx_update(struct gsi_evt_ring *evt_ring, u32 index)
/* Initialize a ring, including allocating DMA memory for its entries */
static int gsi_ring_alloc(struct gsi *gsi, struct gsi_ring *ring, u32 count)
{
- size_t size = count * GSI_RING_ELEMENT_SIZE;
+ u32 size = count * GSI_RING_ELEMENT_SIZE;
struct device *dev = gsi->dev;
dma_addr_t addr;
- /* Hardware requires a 2^n ring size, with alignment equal to size */
+ /* Hardware requires a 2^n ring size, with alignment equal to size.
+ * The size is a power of 2, so we can check alignment using just
+ * the bottom 32 bits for a DMA address of any size.
+ */
ring->virt = dma_alloc_coherent(dev, size, &addr, GFP_KERNEL);
- if (ring->virt && addr % size) {
+ if (ring->virt && lower_32_bits(addr) % size) {
dma_free_coherent(dev, size, ring->virt, addr);
- dev_err(dev, "unable to alloc 0x%zx-aligned ring buffer\n",
+ dev_err(dev, "unable to alloc 0x%x-aligned ring buffer\n",
size);
return -EINVAL; /* Not a good error value, but distinct */
} else if (!ring->virt) {
diff --git a/drivers/net/ipa/ipa_table.c b/drivers/net/ipa/ipa_table.c
index 45e1d68b4694..4f15391aad5f 100644
--- a/drivers/net/ipa/ipa_table.c
+++ b/drivers/net/ipa/ipa_table.c
@@ -662,10 +662,13 @@ int ipa_table_init(struct ipa *ipa)
return -ENOMEM;
/* We put the "zero rule" at the base of our table area. The IPA
- * hardware requires rules to be aligned on a 128-byte boundary.
- * Make sure the allocation satisfies this constraint.
+ * hardware requires route and filter table rules to be aligned
+ * on a 128-byte boundary. As long as the alignment constraint
+ * is a power of 2, we can check alignment using just the bottom
+ * 32 bits for a DMA address of any size.
*/
- if (addr % IPA_TABLE_ALIGN) {
+ BUILD_BUG_ON(!is_power_of_2(IPA_TABLE_ALIGN));
+ if (lower_32_bits(addr) % IPA_TABLE_ALIGN) {
dev_err(dev, "table address %pad not %u-byte aligned\n",
&addr, IPA_TABLE_ALIGN);
dma_free_coherent(dev, size, virt, addr);
