Jason has been running Syzkaller that reported the following WARN_ON: WARNING: CPU: 1 PID: 4738 at drivers/iommu/iommufd/io_pagetable.c:1360 that is a bug of mismatched access pointers.
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 resulted from an overwrite at access->iopt_access_list_id, in iopt_add_access(), called from iommufd_access_change_ioas(), when xa_alloc() succeeds while iopt_calculate_iova_alignment() fails.
Add a new_id in iopt_add_access() and only update iopt_access_list_id when returning successfully.
Fixes: 9227da7816dd ("iommufd: Add iommufd_access_change_ioas(_id) helpers") Cc: stable@vger.kernel.org Reported-by: Jason Gunthorpe jgg@nvidia.com Suggested-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com --- drivers/iommu/iommufd/io_pagetable.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c index 504ac1b01b2d..05fd9d3abf1b 100644 --- a/drivers/iommu/iommufd/io_pagetable.c +++ b/drivers/iommu/iommufd/io_pagetable.c @@ -1330,20 +1330,23 @@ int iopt_disable_large_pages(struct io_pagetable *iopt)
int iopt_add_access(struct io_pagetable *iopt, struct iommufd_access *access) { + u32 new_id; int rc;
down_write(&iopt->domains_rwsem); down_write(&iopt->iova_rwsem); - rc = xa_alloc(&iopt->access_list, &access->iopt_access_list_id, access, - xa_limit_16b, GFP_KERNEL_ACCOUNT); + rc = xa_alloc(&iopt->access_list, &new_id, access, xa_limit_16b, + GFP_KERNEL_ACCOUNT); + if (rc) goto out_unlock;
rc = iopt_calculate_iova_alignment(iopt); if (rc) { - xa_erase(&iopt->access_list, access->iopt_access_list_id); + xa_erase(&iopt->access_list, new_id); goto out_unlock; } + access->iopt_access_list_id = new_id;
out_unlock: up_write(&iopt->iova_rwsem);