Bug 2492727 (CVE-2026-53162)

Summary: CVE-2026-53162 kernel: memcg: use round-robin victim selection in refill_stock
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
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 memory cgroup (memcg) subsystem. When a non-maskable interrupt (NMI) occurs during an update of the system's random number generation state, it can lead to corruption of that state. This issue can result in memory cgroup charge draining, potentially causing system instability or a denial of service.
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Description OSIDB Bzimport 2026-06-25 10:02:36 UTC 
In the Linux kernel, the following vulnerability has been resolved:

memcg: use round-robin victim selection in refill_stock

Harry Yoo reported that get_random_u32_below() is not safe to call in the
nmi context and memcg charge draining can happen in nmi context.

More specifically get_random_u32_below() is neither reentrant- nor
NMI-safe: it acquires a per-cpu local_lock via local_lock_irqsave() on the
batched_entropy_u32 state.  An NMI that lands on a CPU mid-update of the
ChaCha batch state and recurses into the random subsystem would corrupt
that state.  The memcg_stock local_trylock prevents re-entry on the percpu
stock itself, but cannot protect an unrelated subsystem's per-cpu lock.

Replace the random pick with a per-cpu round-robin counter stored in
memcg_stock_pcp and serialized by the same local_trylock that already
guards cached[] and nr_pages[].  No atomics, no random calls, no extra
locks needed.
Comment 1 TEJ RATHI 2026-06-26 07:26:13 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062550-CVE-2026-53162-477b@gregkh/T