ublk: clear VM_MAYWRITE on read-only ublk char device mmap
Summary
| CVE | CVE-2026-89793 |
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| State | PUBLISHED |
|---|
| Assigner | Linux |
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| Source Priority | CVE Program / NVD first with legacy fallback |
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| Published | 2026-09-16 10:16:55 UTC |
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| Updated | 2026-09-16 10:16:55 UTC |
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| Description | In the Linux kernel, the following vulnerability has been resolved:
ublk: clear VM_MAYWRITE on read-only ublk char device mmap
ublk_ch_mmap() rejects mmap requests with VM_WRITE set, but never
clears VM_MAYWRITE on the resulting read-only mapping. This allows
a userspace daemon to mmap the per-queue command buffer PROT_READ,
then upgrade it to PROT_WRITE via mprotect(), since VM_MAYWRITE was
never cleared.
The command buffer holds struct ublksrv_io_desc entries that are
kernel-written ABI; a writable mapping lets an unprivileged daemon
process corrupt fields such as addr, op_flags, nr_sectors, and
start_sector.
Same bug class as the drm/panthor and drm/vc4 VM_MAYWRITE fixes, and
the 2026-08-13 ptp/vmclock fix (a5edadbae57e).
Verified via mprotect() PoC: before the fix, a PROT_READ mapping can
be upgraded to PROT_READ|PROT_WRITE and a write into the command
buffer corrupts io_desc fields (confirmed under KASAN). After the
fix, mprotect() returns -EACCES. |
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Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|
| CNA |
Linux |
Linux |
affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 be41733c24be58e2a1ef718c80fafdfb98a40d5e git |
Not specified |
| CNA |
Linux |
Linux |
affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 5befd06a72216869b607cf7724a4f16c6a2d3999 git |
Not specified |
| CNA |
Linux |
Linux |
affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 e373c1acdbcf88cec533ece9f589020adaed0a78 git |
Not specified |
| CNA |
Linux |
Linux |
affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 fa5e1bc673ca59722608af67b27e65dba0c97926 git |
Not specified |
| CNA |
Linux |
Linux |
affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 6e2b571b0a54755b06e092501913e1dfefe75d6c git |
Not specified |
| CNA |
Linux |
Linux |
affected 6.6.157 semver |
Not specified |
| CNA |
Linux |
Linux |
affected 6.12.110 semver |
Not specified |
| CNA |
Linux |
Linux |
affected 6.18.51 semver |
Not specified |
| CNA |
Linux |
Linux |
affected 7.2.5 semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 6.6.157 6.6.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 6.12.110 6.12.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 6.18.51 6.18.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 7.2.5 7.2.* semver |
Not specified |
| CNA |
Linux |
Linux |
unaffected 7.3-rc2 * original_commit_for_fix |
Not specified |
References
| Reference | Source | Link | Tags |
|---|
| git.kernel.org/stable/c/fa5e1bc673ca59722608af67b27e65dba0c97926 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/e373c1acdbcf88cec533ece9f589020adaed0a78 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/6e2b571b0a54755b06e092501913e1dfefe75d6c |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/5befd06a72216869b607cf7724a4f16c6a2d3999 |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| git.kernel.org/stable/c/be41733c24be58e2a1ef718c80fafdfb98a40d5e |
416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
git.kernel.org |
|
| CVE Program record |
CVE.ORG |
www.cve.org |
canonical |
| NVD vulnerability detail |
NVD |
nvd.nist.gov |
canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.