Overview
About vulnerability
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:
-
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.
-
There is also discussion about removing this count of dst, which might happen in future kernels.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , Oracle Linux 7 ELS , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS
- Affected packages:
- linux-hwe @ 4.15.0 (+8 more)
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:
-
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.
-
There is also discussion about removing this count of dst, which might happen in future kernels.