Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: l2tp: fix tunnel and session refcount leak on seq_file release In pppol2tp_proc_open() and l2tp_dfs_seq_open(), iteration state (pd->tunnel and pd->session) is kept in seq_file private data to allow iteration across multiple read() system calls. However, if userspace closes /proc/net/pppol2tp or /sys/kernel/debug/l2tp/tunnels before reading to end-of-file (EOF), any tunnel or session reference stored in pd->tunnel / pd->session is left un-dropped when seq_file private data is freed. Fix this by dropping any remaining pd->tunnel and pd->session references in pppol2tp_proc_release() and l2tp_dfs_seq_release() when closing the file.

Affected versions

Linux: 0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443 through before bdf83613781956cc39798ed08321f74ab0467f4d (git); 0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443 through before 8c4fde01bcf91f22b9c7ded8c3e14addd7ddd500 (git); 0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443 through before ebe2774e956482dd3c70b8991f6f7654356339e6 (git); 0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443 through before 9006c116dd111d457bf5d074990210f70a4ad2c8 (git); f6104e9ae04462523c372928b1173766a771ef95 (git); 7f8e401f9e612df2a95c1ef76217c00181389bb5 (git); c712ed63e9b33d9a282fbd92ce25c64918c3129f (git); 9a8863e8a8def9d88583cd9c60db38a008e6b8cf (git); 3.16.60 through before 3.17 (semver); 4.16.6 through before 4.17 (semver); 4.17 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.