Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:drm/msm: Fix mmap to include VM_IO and VM_DONTDUMPIn commit 510410bfc034 ("drm/msm: Implement mmap as GEM objectfunction") we switched to a new/cleaner method of doing things. That'sgood, but we missed a little bit.Before that commit, we used to _first_ run through thedrm_gem_mmap_obj() case where `obj->funcs->mmap()` was NULL. That meantthat we ran:  vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;  vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));  vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);...and _then_ we modified those mappings with our own. Now that`obj->funcs->mmap()` is no longer NULL we don't run the defaultcode. It looks like the fact that the vm_flags got VM_IO / VM_DONTDUMPwas important because we're now getting crashes on Chromebooks thatuse ARC++ while logging out. Specifically a crash that looks like this(this is on a 5.10 kernel w/ relevant backports but also seen on a5.15 kernel):  Unable to handle kernel paging request at virtual address ffffffc008000000  Mem abort info:    ESR = 0x96000006    EC = 0x25: DABT (current EL), IL = 32 bits    SET = 0, FnV = 0    EA = 0, S1PTW = 0  Data abort info:    ISV = 0, ISS = 0x00000006    CM = 0, WnR = 0  swapper pgtable: 4k pages, 39-bit VAs, pgdp=000000008293d000  ffffffc008000000] pgd=00000001002b3003, p4d=00000001002b3003,                     pud=00000001002b3003, pmd=0000000000000000  Internal error: Oops: 96000006 [#1] PREEMPT SMP  [...]  CPU: 7 PID: 15734 Comm: crash_dump64 Tainted: G W 5.10.67 #1 [...]  Hardware name: Qualcomm Technologies, Inc. sc7280 IDP SKU2 platform (DT)  pstate: 80400009 (Nzcv daif +PAN -UAO -TCO BTYPE=--)  pc : __arch_copy_to_user+0xc0/0x30c  lr : copyout+0xac/0x14c  [...]  Call trace:   __arch_copy_to_user+0xc0/0x30c   copy_page_to_iter+0x1a0/0x294   process_vm_rw_core+0x240/0x408   process_vm_rw+0x110/0x16c   __arm64_sys_process_vm_readv+0x30/0x3c   el0_svc_common+0xf8/0x250   do_el0_svc+0x30/0x80   el0_svc+0x10/0x1c   el0_sync_handler+0x78/0x108   el0_sync+0x184/0x1c0  Code: f8408423 f80008c3 910020c6 36100082 (b8404423)Let's add the two flags back in.While we're at it, the fact that we aren't running the default meansthat we _don't_ need to clear out VM_PFNMAP, so remove that and savean instruction.NOTE: it was confirmed that VM_IO was the important flag to fix theproblem I was seeing, but adding back VM_DONTDUMP seems like a sanething to do so I'm doing that too.

CREATE(Triage):(User=admin) [CVE-2021-47531 (https://nvd.nist.gov/vuln/detail/CVE-2021-47531)

CVEs

• CVE-2021-47531