In the Linux kernel, the following vulnerability has been resolved:

iommu: Fix dev_iommu memory leak when device_add fails in iommu_mock_device_add

iommu_mock_device_add() first calls iommu_fwspec_init(), which on
success allocates both dev->iommu (via dev_iommu_get()) and
dev->iommu->fwspec. If the subsequent device_add(dev) call fails,
the error path only calls iommu_fwspec_free(dev), which frees
fwspec but leaves dev->iommu still allocated.

This triggers the following kmemleak report when fuzzing with Syzkaller:

BUG: memory leak
unreferenced object 0xffff888011e0a200 (size 192):
  comm "syz.1.1695", pid 24885, jiffies 4295222527
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 ad 4e ad de  .............N..
    ff ff ff ff 00 00 00 00 ff ff ff ff ff ff ff ff  ................
  backtrace (crc 25df5bb3):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4575 [inline]
    slab_alloc_node mm/slub.c:4899 [inline]
    __kmalloc_cache_noprof+0x47a/0x710 mm/slub.c:5415
    kmalloc_noprof include/linux/slab.h:950 [inline]
    kzalloc_noprof include/linux/slab.h:1188 [inline]
    dev_iommu_get+0x10c/0x1a0 drivers/iommu/iommu.c:408
    iommu_fwspec_init+0x288/0x4d0 drivers/iommu/iommu.c:3087
    iommu_mock_device_add+0x46/0xb0 drivers/iommu/iommu.c:385
    mock_dev_create drivers/iommu/iommufd/selftest.c:1025 [inline]
    iommufd_test_mock_domain drivers/iommu/iommufd/selftest.c:1066 [inline]
    iommufd_test+0x2f8a/0x6190 drivers/iommu/iommufd/selftest.c:2072
    iommufd_fops_ioctl+0x367/0x540 drivers/iommu/iommufd/main.c:533
    vfs_ioctl fs/ioctl.c:51 [inline]
    __do_sys_ioctl fs/ioctl.c:597 [inline]
    __se_sys_ioctl fs/ioctl.c:583 [inline]
    __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fix this by calling dev_iommu_free(dev) instead of iommu_fwspec_free(dev)
in the device_add() failure path. dev_iommu_free() frees both fwspec
and the outer dev_iommu struct and clears dev->iommu.