net/sched: act_mirred: don't override retval if we already lost the skb

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_mirred: don't override retval if we already lost the skb If we're redirecting the skb, and haven't called tcf_mirred_forward(), yet, we need to tell the core to drop the skb by setting the retcode to SHOT. If we have called tcf_mirred_forward(), however, the skb is out of our hands and returning SHOT will lead to UaF. Move the retval override to the error path which actually need it.

References

• https://git.kernel.org/stable/c/0117fe0a4615a7c8d30d6ebcbf87332fbe63e6fd
• https://git.kernel.org/stable/c/9d3ef89b6a5e9f2e940de2cef3d543be0be8dec5
• https://git.kernel.org/stable/c/e873e8f7d03a2ee5b77fb1a305c782fed98e2754
• https://git.kernel.org/stable/c/28cdbbd38a4413b8eff53399b3f872fd4e80db9d
• https://git.kernel.org/stable/c/f4e294bbdca8ac8757db436fc82214f3882fc7e7
• https://git.kernel.org/stable/c/166c2c8a6a4dc2e4ceba9e10cfe81c3e469e3210