CVE-2024-26786

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

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.

Weakness

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/9526a46cc0c378d381560279bea9aa34c84298a0
• https://git.kernel.org/stable/c/aeb004c0cd6958e910123a1607634401009c9539
• https://git.kernel.org/stable/c/f1fb745ee0a6fe43f1d84ec369c7e6af2310fda9