CVE-2023-52999

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

net: fix UaF in netns ops registration error path

If netassigngeneric() fails, the current error path in ops_init() tries to clear the gen pointer slot. Anyway, in such error path, the gen pointer itself has not been modified yet, and the existing and accessed one is smaller than the accessed index, causing an out-of-bounds error:

BUG: KASAN: slab-out-of-bounds in ops_init+0x2de/0x320 Write of size 8 at addr ffff888109124978 by task modprobe/1018

CPU: 2 PID: 1018 Comm: modprobe Not tainted 6.2.0-rc2.mptcpae5ac65fbed5+ #1641 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.1-2.fc37 04/01/2014 Call Trace: <TASK> dumpstacklvl+0x6a/0x9f printaddressdescription.constprop.0+0x86/0x2b5 printreport+0x11b/0x1fb kasanreport+0x87/0xc0 opsinit+0x2de/0x320 registerpernetoperations+0x2e4/0x750 registerpernetsubsys+0x24/0x40 tcfregisteraction+0x9f/0x560 dooneinitcall+0xf9/0x570 doinitmodule+0x190/0x650 loadmodule+0x1fa5/0x23c0 _dosysfinitmodule+0x10d/0x1b0 dosyscall64+0x58/0x80 entrySYSCALL64afterhwframe+0x72/0xdc RIP: 0033:0x7f42518f778d Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d cb 56 2c 00 f7 d8 64 89 01 48 RSP: 002b:00007fff96869688 EFLAGS: 00000246 ORIGRAX: 0000000000000139 RAX: ffffffffffffffda RBX: 00005568ef7f7c90 RCX: 00007f42518f778d RDX: 0000000000000000 RSI: 00005568ef41d796 RDI: 0000000000000003 RBP: 00005568ef41d796 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000 R13: 00005568ef7f7d30 R14: 0000000000040000 R15: 0000000000000000 </TASK>

This change addresses the issue by skipping the gen pointer de-reference in the mentioned error-path.

Found by code inspection and verified with explicit error injection on a kasan-enabled kernel.