Bug 2517061 (CVE-2026-74472)

Summary: CVE-2026-74472 kernel: ublk: reset kernel-owned dev_info fields in ublk_ctrl_add_dev()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's `ublk` driver. This vulnerability arises from improper initialization of kernel-owned device information fields when a new `ublk` device is added. A local attacker could exploit this by providing malformed device information, which may lead to a kernel panic, resulting in a Denial of Service (DoS) for the system. This issue can also cause system instability or incorrect reporting of the `ublk` server process.
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Description OSIDB Bzimport 2026-08-15 12:47:38 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ublk: reset kernel-owned dev_info fields in ublk_ctrl_add_dev()

ublk_ctrl_add_dev() memcpy()s the userspace ublksrv_ctrl_dev_info into
ub->dev_info and then fixes up the fields the driver owns, but misses
->state and ->ublksrv_pid.

A device added with ->state = UBLK_S_DEV_LIVE passes the
"->state != UBLK_S_DEV_DEAD" test that ublk_stop_dev_unlocked() uses as its
proxy for "a disk is attached", while ->ub_disk is still NULL, so DEL_DEV
right after ADD_DEV oopses in del_gendisk().  UBLK_S_DEV_QUIESCED plus
UBLK_F_USER_RECOVERY dies one step earlier, in ublk_force_abort_dev().  A
poisoned ->state also gets START_USER_RECOVERY and the char device
read/write path onto a device that was never started, and wedges START_DEV
at -EEXIST.  A poisoned ->ublksrv_pid just makes GET_DEV_INFO report an
unrelated task as the ublk server.

Reset both after the memcpy(), as ublk_detach_disk() does.  Userspace only
ever reads these back, so correcting them silently breaks nothing.

ADD_DEV has copied ->state in unsanitized since ublk was merged, but back
then it was harmless: the gendisk was allocated during ADD_DEV, and both
teardown and the START_DEV -EEXIST check keyed off disk_live() rather than
->state.  The oops became reachable once the disk allocation moved to
START_DEV and those checks switched to ->state.
Comment 1 Mauro Matteo Cascella 2026-08-19 16:42:16 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081535-CVE-2026-74472-fcab@gregkh/T