ipv6: Prevent rt6_insert_exception() for dying fib6_info.
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.18.55, 7.2.9
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: Prevent rt6_insert_exception() for dying fib6_info. Before the cited commit, fib6_nh_flush_exceptions() always set from->exception_bucket_flushed = 1 under rt6_exception_lock to prevent rt6_insert_exception() from inserting a new exception for a dying fib6_info. The flag was replaced with the FIB6_EXCEPTION_BUCKET_FLUSHED bit stored in nh->rt6i_exception_bucket. The problem is that now the bit is only set when the bucket is not NULL and fib6_nh_flush_exceptions() is called from fib6_nh_release() after fib6_ref has already reached zero. If rt6_insert_exception() is called while the target fib6_info is being removed via fib6_purge_rt(), a new exception could be created successfully because rt6_flush_exceptions() no longer sets the bit. This creates a reference cycle between the fib6_info and the exception route, leaking the fib6_info, its nexthop device, and all per-CPU routes in fib6_nh->rt6i_pcpu, which stalls netdev unregistration. [ 34.680602] unregister_netdevice: waiting for gre6 to become free. Usage count = 68 [ 44.920675] unregister_netdevice: waiting for gre6 to become free. Usage count = 68 [ 55.176582] unregister_netdevice: waiting for gre6 to become free. Usage count = 68 Let's call fib6_drop_pcpu_from() before rt6_flush_exceptions(), to set fib6_destroying before rt6_exception_lock, and check f6i->fib6_destroying in rt6_insert_exception(). Note that FIB6_EXCEPTION_BUCKET_FLUSHED logic is dead and we can clean it up in net-next.
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
From cc5c073a693fa6ed7a207b0436114f68cce72434 · fixed in 649ffc76ed5483b2caf35ed90d3787538efc4e53; From cc5c073a693fa6ed7a207b0436114f68cce72434 · fixed in e03e77071e75ce726d877f0a4349a28b6e1f487a; From cc5c073a693fa6ed7a207b0436114f68cce72434 · fixed in 0346ec2f080b40d95ed05b853bb9226289e75212
- Linux Linux
5.3
- KernelLinux
From 5.3.0 · fixed in 6.18.55; From 6.19.0 · fixed in 7.2.9