Bug 2320622 (CVE-2024-50036)

Summary: CVE-2024-50036 kernel: net: do not delay dst_entries_add() in dst_release()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Bug Depends On: 2320896    
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Description OSIDB Bzimport 2024-10-21 20:04:10 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net: do not delay dst_entries_add() in dst_release()

dst_entries_add() uses per-cpu data that might be freed at netns
dismantle from ip6_route_net_exit() calling dst_entries_destroy()

Before ip6_route_net_exit() can be called, we release all
the dsts associated with this netns, via calls to dst_release(),
which waits an rcu grace period before calling dst_destroy()

dst_entries_add() use in dst_destroy() is racy, because
dst_entries_destroy() could have been called already.

Decrementing the number of dsts must happen sooner.

Notes:

1) in CONFIG_XFRM case, dst_destroy() can call
   dst_release_immediate(child), this might also cause UAF
   if the child does not have DST_NOCOUNT set.
   IPSEC maintainers might take a look and see how to address this.

2) There is also discussion about removing this count of dst,
   which might happen in future kernels.
Comment 1 Avinash Hanwate 2024-10-22 10:01:51 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2024102132-CVE-2024-50036-9d91@gregkh/T