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    Subject[PATCH 08/25] memremap: validate the pagemap type passed to devm_memremap_pages
    Date
    Most pgmap types are only supported when certain config options are
    enabled. Check for a type that is valid for the current configuration
    before setting up the pagemap. For this the usage of the 0 type for
    device dax gets replaced with an explicit MEMORY_DEVICE_DEVDAX type.

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    ---
    drivers/dax/device.c | 1 +
    include/linux/memremap.h | 8 ++++++++
    kernel/memremap.c | 22 ++++++++++++++++++++++
    3 files changed, 31 insertions(+)

    diff --git a/drivers/dax/device.c b/drivers/dax/device.c
    index 8465d12fecba..79014baa782d 100644
    --- a/drivers/dax/device.c
    +++ b/drivers/dax/device.c
    @@ -468,6 +468,7 @@ int dev_dax_probe(struct device *dev)
    dev_dax->pgmap.ref = &dev_dax->ref;
    dev_dax->pgmap.kill = dev_dax_percpu_kill;
    dev_dax->pgmap.cleanup = dev_dax_percpu_exit;
    + dev_dax->pgmap.type = MEMORY_DEVICE_DEVDAX;
    addr = devm_memremap_pages(dev, &dev_dax->pgmap);
    if (IS_ERR(addr))
    return PTR_ERR(addr);
    diff --git a/include/linux/memremap.h b/include/linux/memremap.h
    index 995c62c5a48b..0c86f2c5ac9c 100644
    --- a/include/linux/memremap.h
    +++ b/include/linux/memremap.h
    @@ -45,13 +45,21 @@ struct vmem_altmap {
    * wakeup is used to coordinate physical address space management (ex:
    * fs truncate/hole punch) vs pinned pages (ex: device dma).
    *
    + * MEMORY_DEVICE_DEVDAX:
    + * Host memory that has similar access semantics as System RAM i.e. DMA
    + * coherent and supports page pinning. In contrast to
    + * MEMORY_DEVICE_FS_DAX, this memory is access via a device-dax
    + * character device.
    + *
    * MEMORY_DEVICE_PCI_P2PDMA:
    * Device memory residing in a PCI BAR intended for use with Peer-to-Peer
    * transactions.
    */
    enum memory_type {
    + /* 0 is reserved to catch uninitialized type fields */
    MEMORY_DEVICE_PRIVATE = 1,
    MEMORY_DEVICE_FS_DAX,
    + MEMORY_DEVICE_DEVDAX,
    MEMORY_DEVICE_PCI_P2PDMA,
    };

    diff --git a/kernel/memremap.c b/kernel/memremap.c
    index 6e1970719dc2..abda62d1e5a3 100644
    --- a/kernel/memremap.c
    +++ b/kernel/memremap.c
    @@ -157,6 +157,28 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
    pgprot_t pgprot = PAGE_KERNEL;
    int error, nid, is_ram;

    + switch (pgmap->type) {
    + case MEMORY_DEVICE_PRIVATE:
    + if (!IS_ENABLED(CONFIG_DEVICE_PRIVATE)) {
    + WARN(1, "Device private memory not supported\n");
    + return ERR_PTR(-EINVAL);
    + }
    + break;
    + case MEMORY_DEVICE_FS_DAX:
    + if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
    + IS_ENABLED(CONFIG_FS_DAX_LIMITED)) {
    + WARN(1, "File system DAX not supported\n");
    + return ERR_PTR(-EINVAL);
    + }
    + break;
    + case MEMORY_DEVICE_DEVDAX:
    + case MEMORY_DEVICE_PCI_P2PDMA:
    + break;
    + default:
    + WARN(1, "Invalid pgmap type %d\n", pgmap->type);
    + break;
    + }
    +
    if (!pgmap->ref || !pgmap->kill || !pgmap->cleanup) {
    WARN(1, "Missing reference count teardown definition\n");
    return ERR_PTR(-EINVAL);
    --
    2.20.1
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