iommu/dmar: Fix buffer overflow during PCI bus notification [Linux 5.0]

iommu/dmar: Fix buffer overflow during PCI bus notification [Linux 5.0]

This Linux kernel change "iommu/dmar: Fix buffer overflow during PCI bus notification" is included in the Linux 5.0 release. This change is authored by Julia Cartwright <julia [at] ni.com> on Wed Feb 20 16:46:31 2019 +0000. The commit for this change in Linux stable tree is cffaaf0 (patch).

iommu/dmar: Fix buffer overflow during PCI bus notification

Commit 57384592c433 ("iommu/vt-d: Store bus information in RMRR PCI
device path") changed the type of the path data, however, the change in
path type was not reflected in size calculations.  Update to use the
correct type and prevent a buffer overflow.

This bug manifests in systems with deep PCI hierarchies, and can lead to
an overflow of the static allocated buffer (dmar_pci_notify_info_buf),
or can lead to overflow of slab-allocated data.

   BUG: KASAN: global-out-of-bounds in dmar_alloc_pci_notify_info+0x1d5/0x2e0
   Write of size 1 at addr ffffffff90445d80 by task swapper/0/1
   CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W       4.14.87-rt49-02406-gd0a0e96 #1
   Call Trace:
    ? dump_stack+0x46/0x59
    ? print_address_description+0x1df/0x290
    ? dmar_alloc_pci_notify_info+0x1d5/0x2e0
    ? kasan_report+0x256/0x340
    ? dmar_alloc_pci_notify_info+0x1d5/0x2e0
    ? e820__memblock_setup+0xb0/0xb0
    ? dmar_dev_scope_init+0x424/0x48f
    ? __down_write_common+0x1ec/0x230
    ? dmar_dev_scope_init+0x48f/0x48f
    ? dmar_free_unused_resources+0x109/0x109
    ? cpumask_next+0x16/0x20
    ? __kmem_cache_create+0x392/0x430
    ? kmem_cache_create+0x135/0x2f0
    ? e820__memblock_setup+0xb0/0xb0
    ? intel_iommu_init+0x170/0x1848
    ? _raw_spin_unlock_irqrestore+0x32/0x60
    ? migrate_enable+0x27a/0x5b0
    ? sched_setattr+0x20/0x20
    ? migrate_disable+0x1fc/0x380
    ? task_rq_lock+0x170/0x170
    ? try_to_run_init_process+0x40/0x40
    ? locks_remove_file+0x85/0x2f0
    ? dev_prepare_static_identity_mapping+0x78/0x78
    ? rt_spin_unlock+0x39/0x50
    ? lockref_put_or_lock+0x2a/0x40
    ? dput+0x128/0x2f0
    ? __rcu_read_unlock+0x66/0x80
    ? __fput+0x250/0x300
    ? __rcu_read_lock+0x1b/0x30
    ? mntput_no_expire+0x38/0x290
    ? e820__memblock_setup+0xb0/0xb0
    ? pci_iommu_init+0x25/0x63
    ? pci_iommu_init+0x25/0x63
    ? do_one_initcall+0x7e/0x1c0
    ? initcall_blacklisted+0x120/0x120
    ? kernel_init_freeable+0x27b/0x307
    ? rest_init+0xd0/0xd0
    ? kernel_init+0xf/0x120
    ? rest_init+0xd0/0xd0
    ? ret_from_fork+0x1f/0x40
   The buggy address belongs to the variable:
    dmar_pci_notify_info_buf+0x40/0x60

Fixes: 57384592c433 ("iommu/vt-d: Store bus information in RMRR PCI device path")
Signed-off-by: Julia Cartwright <[email protected]>
Signed-off-by: Joerg Roedel <[email protected]>

There are 2 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/iommu/dmar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index dc9f148..58dc70b 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -144,7 +144,7 @@ void dmar_free_dev_scope(struct dmar_dev_scope **devices, int *cnt)
        for (tmp = dev; tmp; tmp = tmp->bus->self)
            level++;

-   size = sizeof(*info) + level * sizeof(struct acpi_dmar_pci_path);
+   size = sizeof(*info) + level * sizeof(info->path[0]);
    if (size <= sizeof(dmar_pci_notify_info_buf)) {
        info = (struct dmar_pci_notify_info *)dmar_pci_notify_info_buf;
    } else {

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