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

sctp: fix possible UAF in sctpv6available()

A lockdep report [1] with CONFIGPROVERCULIST=y hints that sctpv6available() is calling devgetbyindexrcu() and ipv6chk_addr() without holding rcu.

[1] ============================= WARNING: suspicious RCU usage 6.12.0-rc5-virtme #1216 Tainted: G W

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 sctphello/31495: #0: ffff9f1ebbdb7418 (sklock-AFINET6){+.+.}-{0:0}, at: sctpbind (./arch/x86/include/asm/jumplabel.h:27 net/sctp/socket.c:315) sctp

stack backtrace: CPU: 7 UID: 0 PID: 31495 Comm: sctphello Tainted: G W 6.12.0-rc5-virtme #1216 Tainted: [W]=WARN Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: <TASK> dumpstacklvl (lib/dumpstack.c:123) lockdeprcususpicious (kernel/locking/lockdep.c:6822) devgetbyindexrcu (net/core/dev.c:876 (discriminator 7)) sctpv6available (net/sctp/ipv6.c:701) sctp sctpdobind (net/sctp/socket.c:400 (discriminator 1)) sctp sctpbind (net/sctp/socket.c:320) sctp inet6bindsk (net/ipv6/afinet6.c:465) ? securitysocketbind (security/security.c:4581 (discriminator 1)) _sysbind (net/socket.c:1848 net/socket.c:1869) ? douseraddrfault (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 ./include/linux/mm.h:729 arch/x86/mm/fault.c:1340) ? douseraddrfault (./arch/x86/include/asm/preempt.h:84 (discriminator 13) ./include/linux/rcupdate.h:98 (discriminator 13) ./include/linux/rcupdate.h:882 (discriminator 13) ./include/linux/mm.h:729 (discriminator 13) arch/x86/mm/fault.c:1340 (discriminator 13)) _x64sysbind (net/socket.c:1877 (discriminator 1) net/socket.c:1875 (discriminator 1) net/socket.c:1875 (discriminator 1)) dosyscall64 (arch/x86/entry/common.c:52 (discriminator 1) arch/x86/entry/common.c:83 (discriminator 1)) entrySYSCALL64afterhwframe (arch/x86/entry/entry64.S:130) RIP: 0033:0x7f59b934a1e7 Code: 44 00 00 48 8b 15 39 8c 0c 00 f7 d8 64 89 02 b8 ff ff ff ff eb bd 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 b8 31 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 09 8c 0c 00 f7 d8 64 89 01 48

All code

0: 44 00 00 add %r8b,(%rax) 3: 48 8b 15 39 8c 0c 00 mov 0xc8c39(%rip),%rdx # 0xc8c43 a: f7 d8 neg %eax c: 64 89 02 mov %eax,%fs:(%rdx) f: b8 ff ff ff ff mov $0xffffffff,%eax 14: eb bd jmp 0xffffffffffffffd3 16: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1) 1d: 00 00 00 20: 0f 1f 00 nopl (%rax) 23: b8 31 00 00 00 mov $0x31,%eax 28: 0f 05 syscall 2a:* 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax <-- trapping instruction 30: 73 01 jae 0x33 32: c3 ret 33: 48 8b 0d 09 8c 0c 00 mov 0xc8c09(%rip),%rcx # 0xc8c43 3a: f7 d8 neg %eax 3c: 64 89 01 mov %eax,%fs:(%rcx) 3f: 48 rex.W

Code starting with the faulting instruction

0: 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax 6: 73 01 jae 0x9 8: c3 ret 9: 48 8b 0d 09 8c 0c 00 mov 0xc8c09(%rip),%rcx # 0xc8c19 10: f7 d8 neg %eax 12: 64 89 01 mov %eax,%fs:(%rcx) 15: 48 rex.W RSP: 002b:00007ffe2d0ad398 EFLAGS: 00000202 ORIG_RAX: 0000000000000031 RAX: ffffffffffffffda RBX: 00007ffe2d0ad3d0 RCX: 00007f59b934a1e7 RDX: 000000000000001c RSI: 00007ffe2d0ad3d0 RDI: 0000000000000005 RBP: 0000000000000005 R08: 1999999999999999 R09: 0000000000000000 R10: 00007f59b9253298 R11: 000000000000 ---truncated---