Bug 1222779 (CVE-2024-26785)

Summary: VUL-0: CVE-2024-26785: kernel: iommufd: Fix protection fault in iommufd_test_syz_conv_iova
Product: [Novell Products] SUSE Security Incidents Reporter: SMASH SMASH <smash_bz>
Component: IncidentsAssignee: Security Team bot <security-team>
Status: NEW --- QA Contact: Security Team bot <security-team>
Severity: Normal    
Priority: P3 - Medium CC: abergmann, meissner, mhocko, osalvador
Version: unspecified   
Target Milestone: ---   
Hardware: Other   
OS: Other   
URL: https://smash.suse.de/issue/400337/
Whiteboard: CVSSv3.1:SUSE:CVE-2024-26785:5.5:(AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Found By: Security Response Team Services Priority:
Business Priority: Blocker: ---
Marketing QA Status: --- IT Deployment: ---

Description SMASH SMASH 2024-04-15 07:51:31 UTC 
In the Linux kernel, the following vulnerability has been resolved:

iommufd: Fix protection fault in iommufd_test_syz_conv_iova

Syzkaller reported the following bug:

  general protection fault, probably for non-canonical address 0xdffffc0000000038: 0000 [#1] SMP KASAN
  KASAN: null-ptr-deref in range [0x00000000000001c0-0x00000000000001c7]
  Call Trace:
   lock_acquire
   lock_acquire+0x1ce/0x4f0
   down_read+0x93/0x4a0
   iommufd_test_syz_conv_iova+0x56/0x1f0
   iommufd_test_access_rw.isra.0+0x2ec/0x390
   iommufd_test+0x1058/0x1e30
   iommufd_fops_ioctl+0x381/0x510
   vfs_ioctl
   __do_sys_ioctl
   __se_sys_ioctl
   __x64_sys_ioctl+0x170/0x1e0
   do_syscall_x64
   do_syscall_64+0x71/0x140

This is because the new iommufd_access_change_ioas() sets access->ioas to
NULL during its process, so the lock might be gone in a concurrent racing
context.

Fix this by doing the same access->ioas sanity as iommufd_access_rw() and
iommufd_access_pin_pages() functions do.

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-26785
https://www.cve.org/CVERecord?id=CVE-2024-26785
https://git.kernel.org/stable/c/cf7c2789822db8b5efa34f5ebcf1621bc0008d48
https://git.kernel.org/stable/c/fc719ecbca45c9c046640d72baddba3d83e0bc0b
https://bugzilla.redhat.com/show_bug.cgi?id=2273461
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-26785.mbox