In the Linux kernel, the following vulnerability has been resolved: smack: tcp: ipv4, fix incorrect labeling Currently, Smack mirrors the label of incoming tcp/ipv4 connections: when a label 'foo' connects to a label 'bar' with tcp/ipv4, 'foo' always gets 'foo' in returned ipv4 packets. So, 1) returned packets are incorrectly labeled ('foo' instead of 'bar') 2) 'bar' can write to 'foo' without being authorized to write. Here is a scenario how to see this: * Take two machines, let's call them C and S, with active Smack in the default state (no settings, no rules, no labeled hosts, only builtin labels) * At S, add Smack rule 'foo bar w' (labels 'foo' and 'bar' are instantiated at S at this moment) * At S, at label 'bar', launch a program that listens for incoming tcp/ipv4 connections * From C, at label 'foo', connect to the listener at S. (label 'foo' is instantiated at C at this moment) Connection succeedes and works. * Send some data in both directions. * Collect network traffic of this connection. All packets in both directions are labeled with the CIPSO of the label 'foo'. Hence, label 'bar' writes to 'foo' without being authorized, and even without ever being known at C. If anybody cares: exactly the same happens with DCCP. This behavior 1st manifested in release 2.6.29.4 (see Fixes below) and it looks unintentional. At least, no explanation was provided. I changed returned packes label into the 'bar', to bring it into line with the Smack documentation claims.
https://git.kernel.org/stable/c/d3f56c653c65f170b172d3c23120bc64ada645d8
https://git.kernel.org/stable/c/d3703fa94116fed91f64c7d1c7d284fb4369070f
https://git.kernel.org/stable/c/a948ec993541db4ef392b555c37a1186f4d61670
https://git.kernel.org/stable/c/5b4b304f196c070342e32a4752e1fa2e22fc0671
https://git.kernel.org/stable/c/4be9fd15c3c88775bdf6fa37acabe6de85beebff
https://git.kernel.org/stable/c/2fe209d0ad2e2729f7e22b9b31a86cc3ff0db550
https://git.kernel.org/stable/c/0aea09e82eafa50a373fc8a4b84c1d4734751e2c
https://git.kernel.org/stable/c/0776bcf9cb6de46fdd94d10118de1cf9b05f83b9