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nicolincjgunthorpe
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iommufd: Fix iopt_access_list_id overwrite bug
Syzkaller reported the following WARN_ON: WARNING: CPU: 1 PID: 4738 at drivers/iommu/iommufd/io_pagetable.c:1360 Call Trace: iommufd_access_change_ioas+0x2fe/0x4e0 iommufd_access_destroy_object+0x50/0xb0 iommufd_object_remove+0x2a3/0x490 iommufd_object_destroy_user iommufd_access_destroy+0x71/0xb0 iommufd_test_staccess_release+0x89/0xd0 __fput+0x272/0xb50 __fput_sync+0x4b/0x60 __do_sys_close __se_sys_close __x64_sys_close+0x8b/0x110 do_syscall_x64 The mismatch between the access pointer in the list and the passed-in pointer is resulting from an overwrite of access->iopt_access_list_id, in iopt_add_access(). Called from iommufd_access_change_ioas() when xa_alloc() succeeds but iopt_calculate_iova_alignment() fails. Add a new_id in iopt_add_access() and only update iopt_access_list_id when returning successfully. Cc: stable@vger.kernel.org Fixes: 9227da7 ("iommufd: Add iommufd_access_change_ioas(_id) helpers") Link: https://lore.kernel.org/r/2dda7acb25b8562ec5f1310de828ef5da9ef509c.1708636627.git.nicolinc@nvidia.com Reported-by: Jason Gunthorpe <jgg@nvidia.com> Suggested-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>
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drivers/iommu/iommufd/io_pagetable.c

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1330,20 +1330,23 @@ int iopt_disable_large_pages(struct io_pagetable *iopt)
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13311331
int iopt_add_access(struct io_pagetable *iopt, struct iommufd_access *access)
13321332
{
1333+
u32 new_id;
13331334
int rc;
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13351336
down_write(&iopt->domains_rwsem);
13361337
down_write(&iopt->iova_rwsem);
1337-
rc = xa_alloc(&iopt->access_list, &access->iopt_access_list_id, access,
1338-
xa_limit_16b, GFP_KERNEL_ACCOUNT);
1338+
rc = xa_alloc(&iopt->access_list, &new_id, access, xa_limit_16b,
1339+
GFP_KERNEL_ACCOUNT);
1340+
13391341
if (rc)
13401342
goto out_unlock;
13411343

13421344
rc = iopt_calculate_iova_alignment(iopt);
13431345
if (rc) {
1344-
xa_erase(&iopt->access_list, access->iopt_access_list_id);
1346+
xa_erase(&iopt->access_list, new_id);
13451347
goto out_unlock;
13461348
}
1349+
access->iopt_access_list_id = new_id;
13471350

13481351
out_unlock:
13491352
up_write(&iopt->iova_rwsem);

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