From: Kuniyuki Iwashima kuniyu@amazon.com
[ Upstream commit b3abe42e94900bdd045c472f9c9be620ba5ce553 ]
Wei Chen reported a NULL deref in sk_user_ns() [0][1], and Paolo diagnosed the root cause: in unix_diag_get_exact(), the newly allocated skb does not have sk. [2]
We must get the user_ns from the NETLINK_CB(in_skb).sk and pass it to sk_diag_fill().
[0]: BUG: kernel NULL pointer dereference, address: 0000000000000270 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 12bbce067 P4D 12bbce067 PUD 12bc40067 PMD 0 Oops: 0000 [#1] PREEMPT SMP CPU: 0 PID: 27942 Comm: syz-executor.0 Not tainted 6.1.0-rc5-next-20221118 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-48-gd9c812dda519-prebuilt.qemu.org 04/01/2014 RIP: 0010:sk_user_ns include/net/sock.h:920 [inline] RIP: 0010:sk_diag_dump_uid net/unix/diag.c:119 [inline] RIP: 0010:sk_diag_fill+0x77d/0x890 net/unix/diag.c:170 Code: 89 ef e8 66 d4 2d fd c7 44 24 40 00 00 00 00 49 8d 7c 24 18 e8 54 d7 2d fd 49 8b 5c 24 18 48 8d bb 70 02 00 00 e8 43 d7 2d fd <48> 8b 9b 70 02 00 00 48 8d 7b 10 e8 33 d7 2d fd 48 8b 5b 10 48 8d RSP: 0018:ffffc90000d67968 EFLAGS: 00010246 RAX: ffff88812badaa48 RBX: 0000000000000000 RCX: ffffffff840d481d RDX: 0000000000000465 RSI: 0000000000000000 RDI: 0000000000000270 RBP: ffffc90000d679a8 R08: 0000000000000277 R09: 0000000000000000 R10: 0001ffffffffffff R11: 0001c90000d679a8 R12: ffff88812ac03800 R13: ffff88812c87c400 R14: ffff88812ae42210 R15: ffff888103026940 FS: 00007f08b4e6f700(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000270 CR3: 000000012c58b000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> unix_diag_get_exact net/unix/diag.c:285 [inline] unix_diag_handler_dump+0x3f9/0x500 net/unix/diag.c:317 __sock_diag_cmd net/core/sock_diag.c:235 [inline] sock_diag_rcv_msg+0x237/0x250 net/core/sock_diag.c:266 netlink_rcv_skb+0x13e/0x250 net/netlink/af_netlink.c:2564 sock_diag_rcv+0x24/0x40 net/core/sock_diag.c:277 netlink_unicast_kernel net/netlink/af_netlink.c:1330 [inline] netlink_unicast+0x5e9/0x6b0 net/netlink/af_netlink.c:1356 netlink_sendmsg+0x739/0x860 net/netlink/af_netlink.c:1932 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg net/socket.c:734 [inline] ____sys_sendmsg+0x38f/0x500 net/socket.c:2476 ___sys_sendmsg net/socket.c:2530 [inline] __sys_sendmsg+0x197/0x230 net/socket.c:2559 __do_sys_sendmsg net/socket.c:2568 [inline] __se_sys_sendmsg net/socket.c:2566 [inline] __x64_sys_sendmsg+0x42/0x50 net/socket.c:2566 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x4697f9 Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 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 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f08b4e6ec48 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 000000000077bf80 RCX: 00000000004697f9 RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000003 RBP: 00000000004d29e9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000077bf80 R13: 0000000000000000 R14: 000000000077bf80 R15: 00007ffdb36bc6c0 </TASK> Modules linked in: CR2: 0000000000000270
[1]: https://lore.kernel.org/netdev/CAO4mrfdvyjFpokhNsiwZiP-wpdSD0AStcJwfKcKQdAAL... [2]: https://lore.kernel.org/netdev/e04315e7c90d9a75613f3993c2baf2d344eef7eb.came...
Fixes: cae9910e7344 ("net: Add UNIX_DIAG_UID to Netlink UNIX socket diagnostics.") Reported-by: syzbot syzkaller@googlegroups.com Reported-by: Wei Chen harperchen1110@gmail.com Diagnosed-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/unix/diag.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/net/unix/diag.c b/net/unix/diag.c index 9ff64f9df1f3..951b33fa8f5c 100644 --- a/net/unix/diag.c +++ b/net/unix/diag.c @@ -113,14 +113,16 @@ static int sk_diag_show_rqlen(struct sock *sk, struct sk_buff *nlskb) return nla_put(nlskb, UNIX_DIAG_RQLEN, sizeof(rql), &rql); }
-static int sk_diag_dump_uid(struct sock *sk, struct sk_buff *nlskb) +static int sk_diag_dump_uid(struct sock *sk, struct sk_buff *nlskb, + struct user_namespace *user_ns) { - uid_t uid = from_kuid_munged(sk_user_ns(nlskb->sk), sock_i_uid(sk)); + uid_t uid = from_kuid_munged(user_ns, sock_i_uid(sk)); return nla_put(nlskb, UNIX_DIAG_UID, sizeof(uid_t), &uid); }
static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_req *req, - u32 portid, u32 seq, u32 flags, int sk_ino) + struct user_namespace *user_ns, + u32 portid, u32 seq, u32 flags, int sk_ino) { struct nlmsghdr *nlh; struct unix_diag_msg *rep; @@ -166,7 +168,7 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_r goto out_nlmsg_trim;
if ((req->udiag_show & UDIAG_SHOW_UID) && - sk_diag_dump_uid(sk, skb)) + sk_diag_dump_uid(sk, skb, user_ns)) goto out_nlmsg_trim;
nlmsg_end(skb, nlh); @@ -178,7 +180,8 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_r }
static int sk_diag_dump(struct sock *sk, struct sk_buff *skb, struct unix_diag_req *req, - u32 portid, u32 seq, u32 flags) + struct user_namespace *user_ns, + u32 portid, u32 seq, u32 flags) { int sk_ino;
@@ -189,7 +192,7 @@ static int sk_diag_dump(struct sock *sk, struct sk_buff *skb, struct unix_diag_r if (!sk_ino) return 0;
- return sk_diag_fill(sk, skb, req, portid, seq, flags, sk_ino); + return sk_diag_fill(sk, skb, req, user_ns, portid, seq, flags, sk_ino); }
static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) @@ -217,7 +220,7 @@ static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) goto next; if (!(req->udiag_states & (1 << sk->sk_state))) goto next; - if (sk_diag_dump(sk, skb, req, + if (sk_diag_dump(sk, skb, req, sk_user_ns(skb->sk), NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq, NLM_F_MULTI) < 0) @@ -285,7 +288,8 @@ static int unix_diag_get_exact(struct sk_buff *in_skb, if (!rep) goto out;
- err = sk_diag_fill(sk, rep, req, NETLINK_CB(in_skb).portid, + err = sk_diag_fill(sk, rep, req, sk_user_ns(NETLINK_CB(in_skb).sk), + NETLINK_CB(in_skb).portid, nlh->nlmsg_seq, 0, req->udiag_ino); if (err < 0) { nlmsg_free(rep);