CVE-2023-52796

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

ipvlan: add ipvlanroutev6_outbound() helper

Inspired by syzbot reports using a stack of multiple ipvlan devices.

Reduce stack size needed in ipvlanprocessv6outbound() by moving the flowi6 struct used for the route lookup in an non inlined helper. ipvlanroutev6outbound() needs 120 bytes on the stack, immediately reclaimed.

Also make sure ipvlanprocessv4_outbound() is not inlined.

We might also have to lower MAXNESTDEV, because only syzbot uses setups with more than four stacked devices.

BUG: TASK stack guard page was hit at ffffc9000e803ff8 (stack is ffffc9000e804000..ffffc9000e808000) stack guard page: 0000 [#1] SMP KASAN CPU: 0 PID: 13442 Comm: syz-executor.4 Not tainted 6.1.52-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 RIP: 0010:kasancheckrange+0x4/0x2a0 mm/kasan/generic.c:188 Code: 48 01 c6 48 89 c7 e8 db 4e c1 03 31 c0 5d c3 cc 0f 0b eb 02 0f 0b b8 ea ff ff ff 5d c3 cc 00 00 cc cc 00 00 cc cc 55 48 89 e5 <41> 57 41 56 41 55 41 54 53 b0 01 48 85 f6 0f 84 a4 01 00 00 48 89 RSP: 0018:ffffc9000e804000 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817e5bf2 RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff887c6568 RBP: ffffc9000e804000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff92001d0080c R13: dffffc0000000000 R14: ffffffff87e6b100 R15: 0000000000000000 FS: 00007fd0c55826c0(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffc9000e803ff8 CR3: 0000000170ef7000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <#DF> </#DF> <TASK> [<ffffffff81f281d1>] __kasancheckread+0x11/0x20 mm/kasan/shadow.c:31 [<ffffffff817e5bf2>] instrumentatomicread include/linux/instrumented.h:72 [inline] [<ffffffff817e5bf2>] testbit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] [<ffffffff817e5bf2>] cpumasktestcpu include/linux/cpumask.h:506 [inline] [<ffffffff817e5bf2>] cpuonline include/linux/cpumask.h:1092 [inline] [<ffffffff817e5bf2>] tracelockacquire include/trace/events/lock.h:24 [inline] [<ffffffff817e5bf2>] lockacquire+0xe2/0x590 kernel/locking/lockdep.c:5632 [<ffffffff8563221e>] rculockacquire+0x2e/0x40 include/linux/rcupdate.h:306 [<ffffffff8561464d>] rcureadlock include/linux/rcupdate.h:747 [inline] [<ffffffff8561464d>] ip6polroute+0x15d/0x1440 net/ipv6/route.c:2221 [<ffffffff85618120>] ip6polrouteoutput+0x50/0x80 net/ipv6/route.c:2606 [<ffffffff856f65b5>] pollookupfunc include/net/ip6fib.h:584 [inline] [<ffffffff856f65b5>] fib6rulelookup+0x265/0x620 net/ipv6/fib6rules.c:116 [<ffffffff85618009>] ip6routeoutputflagsnoref+0x2d9/0x3a0 net/ipv6/route.c:2638 [<ffffffff8561821a>] ip6routeoutputflags+0xca/0x340 net/ipv6/route.c:2651 [<ffffffff838bd5a3>] ip6routeoutput include/net/ip6route.h:100 [inline] [<ffffffff838bd5a3>] ipvlanprocessv6outbound drivers/net/ipvlan/ipvlancore.c:473 [inline] [<ffffffff838bd5a3>] ipvlanprocessoutbound drivers/net/ipvlan/ipvlancore.c:529 [inline] [<ffffffff838bd5a3>] ipvlanxmitmodel3 drivers/net/ipvlan/ipvlancore.c:602 [inline] [<ffffffff838bd5a3>] ipvlanqueuexmit+0xc33/0x1be0 drivers/net/ipvlan/ipvlancore.c:677 [<ffffffff838c2909>] ipvlanstartxmit+0x49/0x100 drivers/net/ipvlan/ipvlanmain.c:229 [<ffffffff84d03900>] netdevstartxmit include/linux/netdevice.h:4966 [inline] [<ffffffff84d03900>] xmitone net/core/dev.c:3644 [inline] [<ffffffff84d03900>] devhardstartxmit+0x320/0x980 net/core/dev.c:3660 [<ffffffff84d080e2>] __devqueuexmit+0x16b2/0x3370 net/core/dev.c:4324 [<ffffffff855ce4cd>] devqueuexmit include/linux/netdevice.h:3067 [inline] [<ffffffff855ce4cd>] neighhhoutput include/net/neighbour.h:529 [inline] [<f ---truncated---