CVE-2024-50257

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

netfilter: Fix use-after-free in get_info()

ip6table_nat module unload has refcnt warning for UAF. call trace is:

WARNING: CPU: 1 PID: 379 at kernel/module/main.c:853 moduleput+0x6f/0x80 Modules linked in: ip6tablenat(-) CPU: 1 UID: 0 PID: 379 Comm: ip6tables Not tainted 6.12.0-rc4-00047-gc2ee9f594da8-dirty #205 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:moduleput+0x6f/0x80 Call Trace: <TASK> getinfo+0x128/0x180 doip6tgetctl+0x6a/0x430 nfgetsockopt+0x46/0x80 ipv6getsockopt+0xb9/0x100 rawv6getsockopt+0x42/0x190 dosockgetsockopt+0xaa/0x180 _sysgetsockopt+0x70/0xc0 _x64sysgetsockopt+0x20/0x30 dosyscall64+0xa2/0x1a0 entrySYSCALL64after_hwframe+0x77/0x7f

Concurrent execution of module unload and get_info() trigered the warning. The root cause is as follows:

cpu0 cpu1 moduleexit //mod->state = MODULESTATEGOING ip6tablenatexit xtunregistertemplate kfree(t) //removed from templlist getinfo() t = xtfindtablelock listforeachentry(tmpl, &xttemplates[af]...) if (strcmp(tmpl->name, name)) continue; //table not found trymoduleget listforeachentry(t, &xtnet->tables[af]...) return t; //not get refcnt moduleput(t->me) //uaf unregisterpernetsubsys //remove table from xt_net list

While xttable module was going away and has been removed from xttemplates list, we couldnt get refcnt of xttable->me. Check module in xtnet->tables list re-traversal to fix it.