CVE-2024-53042

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

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

There are code paths from which the function is called without holding the RCU read lock, resulting in a suspicious RCU usage warning [1].

Fix by using l3mdevmasterupperifindexbyindex() which will acquire the RCU read lock before calling l3mdevmasterupperifindexbyindex_rcu().

[1] WARNING: suspicious RCU usage

6.12.0-rc3-custom-gac8f72681cf2 #141 Not tainted

net/core/dev.c:876 RCU-list traversed in non-reader section!!

other info that might help us debug this:

rcuscheduleractive = 2, debuglocks = 1 1 lock held by ip/361: #0: ffffffff86fc7cb0 (rtnlmutex){+.+.}-{3:3}, at: rtnetlinkrcvmsg+0x377/0xf60

stack backtrace: CPU: 3 UID: 0 PID: 361 Comm: ip Not tainted 6.12.0-rc3-custom-gac8f72681cf2 #141 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: <TASK> dumpstacklvl+0xba/0x110 lockdeprcususpicious.cold+0x4f/0xd6 devgetbyindexrcu+0x1d3/0x210 l3mdevmasterupperifindexbyindexrcu+0x2b/0xf0 iptunnelbinddev+0x72f/0xa00 iptunnelnewlink+0x368/0x7a0 ipgrenewlink+0x14c/0x170 rtnlnewlink+0x1173/0x19c0 rtnlnewlink+0x6c/0xa0 rtnetlinkrcvmsg+0x3cc/0xf60 netlinkrcvskb+0x171/0x450 netlinkunicast+0x539/0x7f0 netlinksendmsg+0x8c1/0xd80 syssendmsg+0x8f9/0xc20 _syssendmsg+0x197/0x1e0 _syssendmsg+0x122/0x1f0 dosyscall64+0xbb/0x1d0 entrySYSCALL64afterhwframe+0x77/0x7f