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iommufd: Fix struct iommu_hwpt_pgfault init and padding

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The iommu_hwpt_pgfault is used to report IO page fault data to userspace,
but iommufd_fault_fops_read was never zeroing its padding. This leaks the
content of the kernel stack memory to userspace.

Also, the iommufd uAPI requires explicit padding and use of __aligned_u64
to ensure ABI compatibility's with 32 bit.

pahole result, before:
struct iommu_hwpt_pgfault {
        __u32     flags;                /*     0     4 */
        __u32     dev_id;               /*     4     4 */
        __u32     pasid;                /*     8     4 */
        __u32     grpid;                /*    12     4 */
        __u32     perm;                 /*    16     4 */

        /* XXX 4 bytes hole, try to pack */

        __u64     addr;                 /*    24     8 */
        __u32     length;               /*    32     4 */
        __u32     cookie;               /*    36     4 */

        /* size: 40, cachelines: 1, members: 8 */
        /* sum members: 36, holes: 1, sum holes: 4 */
        /* last cacheline: 40 bytes */
};

pahole result, after:
struct iommu_hwpt_pgfault {
        __u32      flags;                /*     0     4 */
        __u32      dev_id;               /*     4     4 */
        __u32      pasid;                /*     8     4 */
        __u32      grpid;                /*    12     4 */
        __u32      perm;                 /*    16     4 */
        __u32      __reserved;           /*    20     4 */
        __u64      addr __attribute__((__aligned__(8))); /*    24     8 */
        __u32      length;               /*    32     4 */
        __u32      cookie;               /*    36     4 */

        /* size: 40, cachelines: 1, members: 9 */
        /* forced alignments: 1 */
        /* last cacheline: 40 bytes */
} __attribute__((__aligned__(8)));

Fixes: c714f15860 ("iommufd: Add fault and response message definitions")
Link: https://patch.msgid.link/r/20250120195051.2450-1-nicolinc@nvidia.com
Cc: stable@vger.kernel.org
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Nicolin Chen
2025-01-20 11:50:51 -08:00
committed by Jason Gunthorpe
parent 3d49020a32
commit e721f619e3
2 changed files with 4 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/uapi/linux/iommufd.h
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@@ -868,6 +868,7 @@ enum iommu_hwpt_pgfault_perm {
* @pasid: Process Address Space ID
* @grpid: Page Request Group Index
* @perm: Combination of enum iommu_hwpt_pgfault_perm
* @__reserved: Must be 0.
* @addr: Fault address
* @length: a hint of how much data the requestor is expecting to fetch. For
* example, if the PRI initiator knows it is going to do a 10MB
@@ -883,7 +884,8 @@ struct iommu_hwpt_pgfault {
__u32 pasid;
__u32 grpid;
__u32 perm;
__u64 addr;
__u32 __reserved;
__aligned_u64 addr;
__u32 length;
__u32 cookie;
};