af_packet: Fix data-races of pkt_sk(sk)->num.

BugLink: https://bugs.launchpad.net/bugs/2029808
[ Upstream commit 822b5a1c17df7e338b9f05d1cfe5764e37c7f74f ]

syzkaller found a data race of pkt_sk(sk)->num.

The value is changed under lock_sock() and po->bind_lock, so we
need READ_ONCE() to access pkt_sk(sk)->num without these locks in
packet_bind_spkt(), packet_bind(), and sk_diag_fill().

Note that WRITE_ONCE() is already added by commit c7d2ef5dd4b0
("net/packet: annotate accesses to po->bind").

BUG: KCSAN: data-race in packet_bind / packet_do_bind

write (marked) to 0xffff88802ffd1cee of 2 bytes by task 7322 on cpu 0:
 packet_do_bind+0x446/0x640 net/packet/af_packet.c:3236
 packet_bind+0x99/0xe0 net/packet/af_packet.c:3321
 __sys_bind+0x19b/0x1e0 net/socket.c:1803
 __do_sys_bind net/socket.c:1814 [inline]
 __se_sys_bind net/socket.c:1812 [inline]
 __x64_sys_bind+0x40/0x50 net/socket.c:1812
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

read to 0xffff88802ffd1cee of 2 bytes by task 7318 on cpu 1:
 packet_bind+0xbf/0xe0 net/packet/af_packet.c:3322
 __sys_bind+0x19b/0x1e0 net/socket.c:1803
 __do_sys_bind net/socket.c:1814 [inline]
 __se_sys_bind net/socket.c:1812 [inline]
 __x64_sys_bind+0x40/0x50 net/socket.c:1812
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

value changed: 0x0300 -> 0x0000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7318 Comm: syz-executor.4 Not tainted 6.3.0-13380-g7fddb5b5300c #4
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

Fixes: 96ec6327144e ("packet: Diag core and basic socket info dumping")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20230524232934.50950-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index a44aed958c7573f51542e98cdefc89a030418a91..da16604b7902dced20a85606cc3e55e0a161f094 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3292,7 +3292,7 @@ static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
        memcpy(name, uaddr->sa_data, sizeof(uaddr->sa_data_min));
        name[sizeof(uaddr->sa_data_min)] = 0;
 
-       return packet_do_bind(sk, name, 0, pkt_sk(sk)->num);
+       return packet_do_bind(sk, name, 0, READ_ONCE(pkt_sk(sk)->num));
 }
 
 static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
@@ -3310,7 +3310,7 @@ static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len
                return -EINVAL;
 
        return packet_do_bind(sk, NULL, sll->sll_ifindex,
-                             sll->sll_protocol ? : pkt_sk(sk)->num);
+                             sll->sll_protocol ? : READ_ONCE(pkt_sk(sk)->num));
 }
 
 static struct proto packet_proto = {

diff --git a/net/packet/diag.c b/net/packet/diag.c
index d704c7bf51b2073f792ff35c1f46fba251dd4761..a68a84574c7394fd86ed6e6e84fe91f53940f6d6 100644 (file)
--- a/net/packet/diag.c
+++ b/net/packet/diag.c
@@ -143,7 +143,7 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb,
        rp = nlmsg_data(nlh);
        rp->pdiag_family = AF_PACKET;
        rp->pdiag_type = sk->sk_type;
-       rp->pdiag_num = ntohs(po->num);
+       rp->pdiag_num = ntohs(READ_ONCE(po->num));
        rp->pdiag_ino = sk_ino;
        sock_diag_save_cookie(sk, rp->pdiag_cookie);