From b3abe42e94900bdd045c472f9c9be620ba5ce553 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Sun, 27 Nov 2022 10:24:11 +0900 Subject: [PATCH 1/2] af_unix: Get user_ns from in_skb in unix_diag_get_exact(). 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: 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 Modules linked in: CR2: 0000000000000270 [1]: https://lore.kernel.org/netdev/CAO4mrfdvyjFpokhNsiwZiP-wpdSD0AStcJwfKcKQdAALQ9_2Qw@mail.gmail.com/ [2]: https://lore.kernel.org/netdev/e04315e7c90d9a75613f3993c2baf2d344eef7eb.camel@redhat.com/ Fixes: cae9910e7344 ("net: Add UNIX_DIAG_UID to Netlink UNIX socket diagnostics.") Reported-by: syzbot Reported-by: Wei Chen Diagnosed-by: Paolo Abeni Signed-off-by: Kuniyuki Iwashima Signed-off-by: Paolo Abeni --- 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 105f522a89fe..616b55c5b890 100644 --- a/net/unix/diag.c +++ b/net/unix/diag.c @@ -114,14 +114,16 @@ 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; @@ -167,7 +169,7 @@ 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); @@ -179,7 +181,8 @@ 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; @@ -190,7 +193,7 @@ 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) @@ -214,7 +217,7 @@ 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) { @@ -282,7 +285,8 @@ 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); From ac011361bd4f6206b36d2a242500239881bf8d2a Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Sun, 27 Nov 2022 10:24:12 +0900 Subject: [PATCH 2/2] af_unix: Add test for sock_diag and UDIAG_SHOW_UID. The test prog dumps a single AF_UNIX socket's UID with and without unshare(CLONE_NEWUSER) and checks if it matches the result of getuid(). Without the preceding patch, the test prog is killed by a NULL deref in sk_diag_dump_uid(). # ./diag_uid TAP version 13 1..2 # Starting 2 tests from 3 test cases. # RUN diag_uid.uid.1 ... BUG: kernel NULL pointer dereference, address: 0000000000000270 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 105212067 P4D 105212067 PUD 1051fe067 PMD 0 Oops: 0000 [#1] PREEMPT SMP NOPTI Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.amzn2022.0.1 04/01/2014 RIP: 0010:sk_diag_fill (./include/net/sock.h:920 net/unix/diag.c:119 net/unix/diag.c:170) ... # 1: Test terminated unexpectedly by signal 9 # FAIL diag_uid.uid.1 not ok 1 diag_uid.uid.1 # RUN diag_uid.uid_unshare.1 ... # 1: Test terminated by timeout # FAIL diag_uid.uid_unshare.1 not ok 2 diag_uid.uid_unshare.1 # FAILED: 0 / 2 tests passed. # Totals: pass:0 fail:2 xfail:0 xpass:0 skip:0 error:0 With the patch, the test succeeds. # ./diag_uid TAP version 13 1..2 # Starting 2 tests from 3 test cases. # RUN diag_uid.uid.1 ... # OK diag_uid.uid.1 ok 1 diag_uid.uid.1 # RUN diag_uid.uid_unshare.1 ... # OK diag_uid.uid_unshare.1 ok 2 diag_uid.uid_unshare.1 # PASSED: 2 / 2 tests passed. # Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0 Signed-off-by: Kuniyuki Iwashima Signed-off-by: Paolo Abeni --- tools/testing/selftests/net/.gitignore | 1 + tools/testing/selftests/net/af_unix/Makefile | 2 +- .../testing/selftests/net/af_unix/diag_uid.c | 178 ++++++++++++++++++ 3 files changed, 180 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/net/af_unix/diag_uid.c diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore index 3d7adee7a3e6..ff8fe93f679c 100644 --- a/tools/testing/selftests/net/.gitignore +++ b/tools/testing/selftests/net/.gitignore @@ -1,6 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only bind_bhash cmsg_sender +diag_uid fin_ack_lat gro hwtstamp_config diff --git a/tools/testing/selftests/net/af_unix/Makefile b/tools/testing/selftests/net/af_unix/Makefile index 969620ae9928..1e4b397cece6 100644 --- a/tools/testing/selftests/net/af_unix/Makefile +++ b/tools/testing/selftests/net/af_unix/Makefile @@ -1,3 +1,3 @@ -TEST_GEN_PROGS := test_unix_oob unix_connect +TEST_GEN_PROGS := diag_uid test_unix_oob unix_connect include ../../lib.mk diff --git a/tools/testing/selftests/net/af_unix/diag_uid.c b/tools/testing/selftests/net/af_unix/diag_uid.c new file mode 100644 index 000000000000..5b88f7129fea --- /dev/null +++ b/tools/testing/selftests/net/af_unix/diag_uid.c @@ -0,0 +1,178 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright Amazon.com Inc. or its affiliates. */ + +#define _GNU_SOURCE +#include + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "../../kselftest_harness.h" + +FIXTURE(diag_uid) +{ + int netlink_fd; + int unix_fd; + __u32 inode; + __u64 cookie; +}; + +FIXTURE_VARIANT(diag_uid) +{ + int unshare; + int udiag_show; +}; + +FIXTURE_VARIANT_ADD(diag_uid, uid) +{ + .unshare = 0, + .udiag_show = UDIAG_SHOW_UID +}; + +FIXTURE_VARIANT_ADD(diag_uid, uid_unshare) +{ + .unshare = CLONE_NEWUSER, + .udiag_show = UDIAG_SHOW_UID +}; + +FIXTURE_SETUP(diag_uid) +{ + struct stat file_stat; + socklen_t optlen; + int ret; + + if (variant->unshare) + ASSERT_EQ(unshare(variant->unshare), 0); + + self->netlink_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG); + ASSERT_NE(self->netlink_fd, -1); + + self->unix_fd = socket(AF_UNIX, SOCK_STREAM, 0); + ASSERT_NE(self->unix_fd, -1); + + ret = fstat(self->unix_fd, &file_stat); + ASSERT_EQ(ret, 0); + + self->inode = file_stat.st_ino; + + optlen = sizeof(self->cookie); + ret = getsockopt(self->unix_fd, SOL_SOCKET, SO_COOKIE, &self->cookie, &optlen); + ASSERT_EQ(ret, 0); +} + +FIXTURE_TEARDOWN(diag_uid) +{ + close(self->netlink_fd); + close(self->unix_fd); +} + +int send_request(struct __test_metadata *_metadata, + FIXTURE_DATA(diag_uid) *self, + const FIXTURE_VARIANT(diag_uid) *variant) +{ + struct { + struct nlmsghdr nlh; + struct unix_diag_req udr; + } req = { + .nlh = { + .nlmsg_len = sizeof(req), + .nlmsg_type = SOCK_DIAG_BY_FAMILY, + .nlmsg_flags = NLM_F_REQUEST + }, + .udr = { + .sdiag_family = AF_UNIX, + .udiag_ino = self->inode, + .udiag_cookie = { + (__u32)self->cookie, + (__u32)(self->cookie >> 32) + }, + .udiag_show = variant->udiag_show + } + }; + struct sockaddr_nl nladdr = { + .nl_family = AF_NETLINK + }; + struct iovec iov = { + .iov_base = &req, + .iov_len = sizeof(req) + }; + struct msghdr msg = { + .msg_name = &nladdr, + .msg_namelen = sizeof(nladdr), + .msg_iov = &iov, + .msg_iovlen = 1 + }; + + return sendmsg(self->netlink_fd, &msg, 0); +} + +void render_response(struct __test_metadata *_metadata, + struct unix_diag_req *udr, __u32 len) +{ + unsigned int rta_len = len - NLMSG_LENGTH(sizeof(*udr)); + struct rtattr *attr; + uid_t uid; + + ASSERT_GT(len, sizeof(*udr)); + ASSERT_EQ(udr->sdiag_family, AF_UNIX); + + attr = (struct rtattr *)(udr + 1); + ASSERT_NE(RTA_OK(attr, rta_len), 0); + ASSERT_EQ(attr->rta_type, UNIX_DIAG_UID); + + uid = *(uid_t *)RTA_DATA(attr); + ASSERT_EQ(uid, getuid()); +} + +void receive_response(struct __test_metadata *_metadata, + FIXTURE_DATA(diag_uid) *self) +{ + long buf[8192 / sizeof(long)]; + struct sockaddr_nl nladdr = { + .nl_family = AF_NETLINK + }; + struct iovec iov = { + .iov_base = buf, + .iov_len = sizeof(buf) + }; + struct msghdr msg = { + .msg_name = &nladdr, + .msg_namelen = sizeof(nladdr), + .msg_iov = &iov, + .msg_iovlen = 1 + }; + struct unix_diag_req *udr; + struct nlmsghdr *nlh; + int ret; + + ret = recvmsg(self->netlink_fd, &msg, 0); + ASSERT_GT(ret, 0); + + nlh = (struct nlmsghdr *)buf; + ASSERT_NE(NLMSG_OK(nlh, ret), 0); + ASSERT_EQ(nlh->nlmsg_type, SOCK_DIAG_BY_FAMILY); + + render_response(_metadata, NLMSG_DATA(nlh), nlh->nlmsg_len); + + nlh = NLMSG_NEXT(nlh, ret); + ASSERT_EQ(NLMSG_OK(nlh, ret), 0); +} + +TEST_F(diag_uid, 1) +{ + int ret; + + ret = send_request(_metadata, self, variant); + ASSERT_GT(ret, 0); + + receive_response(_metadata, self); +} + +TEST_HARNESS_MAIN