CVE-2024-36902

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

ipv6: fib6rules: avoid possible NULL dereference in fib6rule_action()

syzbot is able to trigger the following crash [1], caused by unsafe ip6dstidev() use.

Indeed ip6dstidev() can return NULL, and must always be checked.

[1]

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 PID: 31648 Comm: syz-executor.0 Not tainted 6.9.0-rc4-next-20240417-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 RIP: 0010:__fib6ruleaction net/ipv6/fib6_rules.c:237 [inline] RIP: 0010:fib6ruleaction+0x241/0x7b0 net/ipv6/fib6rules.c:267 Code: 02 00 00 49 8d 9f d8 00 00 00 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 f9 32 bf f7 48 8b 1b 48 89 d8 48 c1 e8 03 <42> 80 3c 20 00 74 08 48 89 df e8 e0 32 bf f7 4c 8b 03 48 89 ef 4c RSP: 0018:ffffc9000fc1f2f0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1a772f98c8186700 RDX: 0000000000000003 RSI: ffffffff8bcac4e0 RDI: ffffffff8c1f9760 RBP: ffff8880673fb980 R08: ffffffff8fac15ef R09: 1ffffffff1f582bd R10: dffffc0000000000 R11: fffffbfff1f582be R12: dffffc0000000000 R13: 0000000000000080 R14: ffff888076509000 R15: ffff88807a029a00 FS: 00007f55e82ca6c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b31d23000 CR3: 0000000022b66000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> fibruleslookup+0x62c/0xdb0 net/core/fibrules.c:317 fib6rulelookup+0x1fd/0x790 net/ipv6/fib6rules.c:108 ip6routeoutputflagsnoref net/ipv6/route.c:2637 [inline] ip6routeoutputflags+0x38e/0x610 net/ipv6/route.c:2649 ip6routeoutput include/net/ip6route.h:93 [inline] ip6dstlookuptail+0x189/0x11a0 net/ipv6/ip6output.c:1120 ip6dstlookupflow+0xb9/0x180 net/ipv6/ip6output.c:1250 sctpv6getdst+0x792/0x1e20 net/sctp/ipv6.c:326 sctptransportroute+0x12c/0x2e0 net/sctp/transport.c:455 sctpassocaddpeer+0x614/0x15c0 net/sctp/associola.c:662 sctpconnectnewasoc+0x31d/0x6c0 net/sctp/socket.c:1099 __sctpconnect+0x66d/0xe30 net/sctp/socket.c:1197 sctpconnect net/sctp/socket.c:4819 [inline] sctpinetconnect+0x149/0x1f0 net/sctp/socket.c:4834 __sysconnectfile net/socket.c:2048 [inline] __sys_connect+0x2df/0x310 net/socket.c:2065 __dosysconnect net/socket.c:2075 [inline] __sesysconnect net/socket.c:2072 [inline] __x64sysconnect+0x7a/0x90 net/socket.c:2072 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0xf5/0x240 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x77/0x7f