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llc: only change llc->dev when bind() succeeds 

My latest patch, attempting to fix the refcount leak in a minimal
way turned out to add a new bug.

Whenever the bind operation fails before we attempt to grab
a reference count on a device, we might release the device refcount
of a prior successful bind() operation.

syzbot was not happy about this [1].

Note to stable teams:

Make sure commit b37a466837 ("netdevice: add the case if dev is NULL")
is already present in your trees.

[1]
general protection fault, probably for non-canonical address 0xdffffc0000000070: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000380-0x0000000000000387]
CPU: 1 PID: 3590 Comm: syz-executor361 Tainted: G        W         5.17.0-syzkaller-04796-g169e77764adc #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:llc_ui_connect+0x400/0xcb0 net/llc/af_llc.c:500
Code: 80 3c 02 00 0f 85 fc 07 00 00 4c 8b a5 38 05 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d bc 24 80 03 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 a9 07 00 00 49 8b b4 24 80 03 00 00 4c 89 f2 48
RSP: 0018:ffffc900038cfcc0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8880756eb600 RCX: 0000000000000000
RDX: 0000000000000070 RSI: ffffc900038cfe3e RDI: 0000000000000380
RBP: ffff888015ee5000 R08: 0000000000000001 R09: ffff888015ee5535
R10: ffffed1002bdcaa6 R11: 0000000000000000 R12: 0000000000000000
R13: ffffc900038cfe37 R14: ffffc900038cfe38 R15: ffff888015ee5012
FS:  0000555555acd300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000280 CR3: 0000000077db6000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __sys_connect_file+0x155/0x1a0 net/socket.c:1900
 __sys_connect+0x161/0x190 net/socket.c:1917
 __do_sys_connect net/socket.c:1927 [inline]
 __se_sys_connect net/socket.c:1924 [inline]
 __x64_sys_connect+0x6f/0xb0 net/socket.c:1924
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f016acb90b9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd417947f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f016acb90b9
RDX: 0000000000000010 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 00007f016ac7d0a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f016ac7d130
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:llc_ui_connect+0x400/0xcb0 net/llc/af_llc.c:500

Fixes: 764f4eb684 ("llc: fix netdevice reference leaks in llc_ui_bind()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: 赵子轩 <beraphin@gmail.com>
Cc: Stoyan Manolov <smanolov@suse.de>
Link: https://lore.kernel.org/r/20220325035827.360418-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2022-03-24 20:58:27 -07:00 committed by Jakub Kicinski
parent 371d1ccf43
commit 2d327a79ee
1 changed files with 34 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
net/llc/af_llc.c
View File

@ -275,6 +275,7 @@ static int llc_ui_autobind(struct socket *sock, struct sockaddr_llc *addr)
{
struct sock *sk = sock->sk;
struct llc_sock *llc = llc_sk(sk);
struct net_device *dev = NULL;
struct llc_sap *sap;
int rc = -EINVAL;
@ -286,16 +287,15 @@ static int llc_ui_autobind(struct socket *sock, struct sockaddr_llc *addr)
goto out;
rc = -ENODEV;
if (sk->sk_bound_dev_if) {
llc->dev = dev_get_by_index(&init_net, sk->sk_bound_dev_if);
if (llc->dev && addr->sllc_arphrd != llc->dev->type) {
dev_put(llc->dev);
llc->dev = NULL;
dev = dev_get_by_index(&init_net, sk->sk_bound_dev_if);
if (dev && addr->sllc_arphrd != dev->type) {
dev_put(dev);
dev = NULL;
}
} else
llc->dev = dev_getfirstbyhwtype(&init_net, addr->sllc_arphrd);
if (!llc->dev)
dev = dev_getfirstbyhwtype(&init_net, addr->sllc_arphrd);
if (!dev)
goto out;
netdev_tracker_alloc(llc->dev, &llc->dev_tracker, GFP_KERNEL);
rc = -EUSERS;
llc->laddr.lsap = llc_ui_autoport();
if (!llc->laddr.lsap)
@ -304,6 +304,12 @@ static int llc_ui_autobind(struct socket *sock, struct sockaddr_llc *addr)
sap = llc_sap_open(llc->laddr.lsap, NULL);
if (!sap)
goto out;
/* Note: We do not expect errors from this point. */
llc->dev = dev;
netdev_tracker_alloc(llc->dev, &llc->dev_tracker, GFP_KERNEL);
dev = NULL;
memcpy(llc->laddr.mac, llc->dev->dev_addr, IFHWADDRLEN);
memcpy(&llc->addr, addr, sizeof(llc->addr));
/* assign new connection to its SAP */
@ -311,10 +317,7 @@ static int llc_ui_autobind(struct socket *sock, struct sockaddr_llc *addr)
sock_reset_flag(sk, SOCK_ZAPPED);
rc = 0;
out:
if (rc) {
dev_put_track(llc->dev, &llc->dev_tracker);
llc->dev = NULL;
}
dev_put(dev);
return rc;
}
@ -337,6 +340,7 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
struct sockaddr_llc *addr = (struct sockaddr_llc *)uaddr;
struct sock *sk = sock->sk;
struct llc_sock *llc = llc_sk(sk);
struct net_device *dev = NULL;
struct llc_sap *sap;
int rc = -EINVAL;
@ -352,25 +356,27 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
rc = -ENODEV;
rcu_read_lock();
if (sk->sk_bound_dev_if) {
llc->dev = dev_get_by_index_rcu(&init_net, sk->sk_bound_dev_if);
if (llc->dev) {
dev = dev_get_by_index_rcu(&init_net, sk->sk_bound_dev_if);
if (dev) {
if (is_zero_ether_addr(addr->sllc_mac))
memcpy(addr->sllc_mac, llc->dev->dev_addr,
memcpy(addr->sllc_mac, dev->dev_addr,
IFHWADDRLEN);
if (addr->sllc_arphrd != llc->dev->type ||
if (addr->sllc_arphrd != dev->type ||
!ether_addr_equal(addr->sllc_mac,
llc->dev->dev_addr)) {
dev->dev_addr)) {
rc = -EINVAL;
llc->dev = NULL;
dev = NULL;
}
}
} else
llc->dev = dev_getbyhwaddr_rcu(&init_net, addr->sllc_arphrd,
} else {
dev = dev_getbyhwaddr_rcu(&init_net, addr->sllc_arphrd,
addr->sllc_mac);
dev_hold_track(llc->dev, &llc->dev_tracker, GFP_ATOMIC);
}
dev_hold(dev);
rcu_read_unlock();
if (!llc->dev)
if (!dev)
goto out;
if (!addr->sllc_sap) {
rc = -EUSERS;
addr->sllc_sap = llc_ui_autoport();
@ -402,6 +408,12 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
goto out_put;
}
}
/* Note: We do not expect errors from this point. */
llc->dev = dev;
netdev_tracker_alloc(llc->dev, &llc->dev_tracker, GFP_KERNEL);
dev = NULL;
llc->laddr.lsap = addr->sllc_sap;
memcpy(llc->laddr.mac, addr->sllc_mac, IFHWADDRLEN);
memcpy(&llc->addr, addr, sizeof(llc->addr));
@ -412,10 +424,7 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
out_put:
llc_sap_put(sap);
out:
if (rc) {
dev_put_track(llc->dev, &llc->dev_tracker);
llc->dev = NULL;
}
dev_put(dev);
release_sock(sk);
return rc;
}