Bug 2401575 (CVE-2022-50506)

Summary: CVE-2022-50506 kernel: drbd: only clone bio if we have a backing device
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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Description OSIDB Bzimport 2025-10-04 16:08:13 UTC 
In the Linux kernel, the following vulnerability has been resolved:

drbd: only clone bio if we have a backing device

Commit c347a787e34cb (drbd: set ->bi_bdev in drbd_req_new) moved a
bio_set_dev call (which has since been removed) to "earlier", from
drbd_request_prepare to drbd_req_new.

The problem is that this accesses device->ldev->backing_bdev, which is
not NULL-checked at this point. When we don't have an ldev (i.e. when
the DRBD device is diskless), this leads to a null pointer deref.

So, only allocate the private_bio if we actually have a disk. This is
also a small optimization, since we don't clone the bio to only to
immediately free it again in the diskless case.
Comment 1 Alexander B 2025-10-06 11:03:25 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025100422-CVE-2022-50506-1642@gregkh/T