CVE-2024-50304

In the Linux kernel, the following vulnerability has been resolved:

ipv4: iptunnel: Fix suspicious RCU usage warning in iptunnel_find()

The per-netns IP tunnel hash table is protected by the RTNL mutex and iptunnelfind() is only called from the control path where the mutex is taken.

Add a lockdep expression to hlistforeachentryrcu() in iptunnelfind() in order to validate that the mutex is held and to silence the suspicious RCU usage warning [1].

[1] WARNING: suspicious RCU usage

6.12.0-rc3-custom-gd95d9a31aceb #139 Not tainted

net/ipv4/ip_tunnel.c:221 RCU-list traversed in non-reader section!!

other info that might help us debug this:

rcuscheduleractive = 2, debuglocks = 1 1 lock held by ip/362: #0: ffffffff86fc7cb0 (rtnlmutex){+.+.}-{3:3}, at: rtnetlinkrcvmsg+0x377/0xf60

stack backtrace: CPU: 12 UID: 0 PID: 362 Comm: ip Not tainted 6.12.0-rc3-custom-gd95d9a31aceb #139 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: <TASK> dumpstacklvl+0xba/0x110 lockdeprcususpicious.cold+0x4f/0xd6 iptunnelfind+0x435/0x4d0 iptunnelnewlink+0x517/0x7a0 ipgre_newlink+0x14c/0x170 __rtnlnewlink+0x1173/0x19c0 rtnlnewlink+0x6c/0xa0 rtnetlinkrcvmsg+0x3cc/0xf60 netlinkrcvskb+0x171/0x450 netlinkunicast+0x539/0x7f0 netlinksendmsg+0x8c1/0xd80 ____sys_sendmsg+0x8f9/0xc20 ___sys_sendmsg+0x197/0x1e0 _syssendmsg+0x122/0x1f0 dosyscall64+0xbb/0x1d0 entrySYSCALL64afterhwframe+0x77/0x7f