Bug 2502436 (CVE-2026-63955) - CVE-2026-63955 kernel: mm/vmalloc: do not trigger BUG() on BH disabled context
Summary: CVE-2026-63955 kernel: mm/vmalloc: do not trigger BUG() on BH disabled context
Keywords:
Status: NEW
Alias: CVE-2026-63955
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-07-19 16:08 UTC by OSIDB Bzimport
Modified: 2026-07-21 16:13 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


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Description OSIDB Bzimport 2026-07-19 16:08:02 UTC
In the Linux kernel, the following vulnerability has been resolved:

mm/vmalloc: do not trigger BUG() on BH disabled context

__get_vm_area_node() currently triggers a BUG() if in_interrupt() returns
true.  However, in_interrupt() also reports true when BH are disabled.

The bridge code can call rhashtable_lookup_insert_fast() with bottom
halves disabled:

__vlan_add()
 -> br_fdb_add_local()
  spin_lock_bh(&br->hash_lock); <-- Disable BH
   -> fdb_add_local()
    -> fdb_create()
     -> rhashtable_lookup_insert_fast()
      -> kvmalloc()
       -> vmalloc()
        -> __get_vm_area_node()
         -> BUG_ON(in_interrupt())
  spin_unlock_bh(&br->hash_lock)

this triggers the BUG() despite the caller not being in NMI or
hard IRQ context.

Replace the in_interrupt() check with in_nmi() || in_hardirq().

Comment 1 Mauro Matteo Cascella 2026-07-21 16:06:31 UTC
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071956-CVE-2026-63955-bf37@gregkh/T


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