4.19-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit dad555c816a50c6a6a8a86be1f9177673918c647 ]
syzbot was able to trick llc_ui_sendmsg(), allocating an skb with no headroom, but subsequently trying to push 14 bytes of Ethernet header [1]
Like some others, llc_ui_sendmsg() releases the socket lock before calling sock_alloc_send_skb(). Then it acquires it again, but does not redo all the sanity checks that were performed.
This fix:
- Uses LL_RESERVED_SPACE() to reserve space. - Check all conditions again after socket lock is held again. - Do not account Ethernet header for mtu limitation.
[1]
skbuff: skb_under_panic: text:ffff800088baa334 len:1514 put:14 head:ffff0000c9c37000 data:ffff0000c9c36ff2 tail:0x5dc end:0x6c0 dev:bond0
kernel BUG at net/core/skbuff.c:193 ! Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 6875 Comm: syz-executor.0 Not tainted 6.7.0-rc8-syzkaller-00101-g0802e17d9aca-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : skb_panic net/core/skbuff.c:189 [inline] pc : skb_under_panic+0x13c/0x140 net/core/skbuff.c:203 lr : skb_panic net/core/skbuff.c:189 [inline] lr : skb_under_panic+0x13c/0x140 net/core/skbuff.c:203 sp : ffff800096f97000 x29: ffff800096f97010 x28: ffff80008cc8d668 x27: dfff800000000000 x26: ffff0000cb970c90 x25: 00000000000005dc x24: ffff0000c9c36ff2 x23: ffff0000c9c37000 x22: 00000000000005ea x21: 00000000000006c0 x20: 000000000000000e x19: ffff800088baa334 x18: 1fffe000368261ce x17: ffff80008e4ed000 x16: ffff80008a8310f8 x15: 0000000000000001 x14: 1ffff00012df2d58 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000001 x10: 0000000000ff0100 x9 : e28a51f1087e8400 x8 : e28a51f1087e8400 x7 : ffff80008028f8d0 x6 : 0000000000000000 x5 : 0000000000000001 x4 : 0000000000000001 x3 : ffff800082b78714 x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000089 Call trace: skb_panic net/core/skbuff.c:189 [inline] skb_under_panic+0x13c/0x140 net/core/skbuff.c:203 skb_push+0xf0/0x108 net/core/skbuff.c:2451 eth_header+0x44/0x1f8 net/ethernet/eth.c:83 dev_hard_header include/linux/netdevice.h:3188 [inline] llc_mac_hdr_init+0x110/0x17c net/llc/llc_output.c:33 llc_sap_action_send_xid_c+0x170/0x344 net/llc/llc_s_ac.c:85 llc_exec_sap_trans_actions net/llc/llc_sap.c:153 [inline] llc_sap_next_state net/llc/llc_sap.c:182 [inline] llc_sap_state_process+0x1ec/0x774 net/llc/llc_sap.c:209 llc_build_and_send_xid_pkt+0x12c/0x1c0 net/llc/llc_sap.c:270 llc_ui_sendmsg+0x7bc/0xb1c net/llc/af_llc.c:997 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] sock_sendmsg+0x194/0x274 net/socket.c:767 splice_to_socket+0x7cc/0xd58 fs/splice.c:881 do_splice_from fs/splice.c:933 [inline] direct_splice_actor+0xe4/0x1c0 fs/splice.c:1142 splice_direct_to_actor+0x2a0/0x7e4 fs/splice.c:1088 do_splice_direct+0x20c/0x348 fs/splice.c:1194 do_sendfile+0x4bc/0xc70 fs/read_write.c:1254 __do_sys_sendfile64 fs/read_write.c:1322 [inline] __se_sys_sendfile64 fs/read_write.c:1308 [inline] __arm64_sys_sendfile64+0x160/0x3b4 fs/read_write.c:1308 __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155 el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595 Code: aa1803e6 aa1903e7 a90023f5 94792f6a (d4210000)
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-and-tested-by: syzbot+2a7024e9502df538e8ef@syzkaller.appspotmail.com Signed-off-by: Eric Dumazet edumazet@google.com Reviewed-by: Kuniyuki Iwashima kuniyu@amazon.com Link: https://lore.kernel.org/r/20240118183625.4007013-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/llc/af_llc.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c index 5cba9199c3c9..a5c104ea477c 100644 --- a/net/llc/af_llc.c +++ b/net/llc/af_llc.c @@ -926,14 +926,15 @@ static int llc_ui_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, */ static int llc_ui_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) { + DECLARE_SOCKADDR(struct sockaddr_llc *, addr, msg->msg_name); struct sock *sk = sock->sk; struct llc_sock *llc = llc_sk(sk); - DECLARE_SOCKADDR(struct sockaddr_llc *, addr, msg->msg_name); int flags = msg->msg_flags; int noblock = flags & MSG_DONTWAIT; + int rc = -EINVAL, copied = 0, hdrlen, hh_len; struct sk_buff *skb = NULL; + struct net_device *dev; size_t size = 0; - int rc = -EINVAL, copied = 0, hdrlen;
dprintk("%s: sending from %02X to %02X\n", __func__, llc->laddr.lsap, llc->daddr.lsap); @@ -953,22 +954,29 @@ static int llc_ui_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) if (rc) goto out; } - hdrlen = llc->dev->hard_header_len + llc_ui_header_len(sk, addr); + dev = llc->dev; + hh_len = LL_RESERVED_SPACE(dev); + hdrlen = llc_ui_header_len(sk, addr); size = hdrlen + len; - if (size > llc->dev->mtu) - size = llc->dev->mtu; + size = min_t(size_t, size, READ_ONCE(dev->mtu)); copied = size - hdrlen; rc = -EINVAL; if (copied < 0) goto out; release_sock(sk); - skb = sock_alloc_send_skb(sk, size, noblock, &rc); + skb = sock_alloc_send_skb(sk, hh_len + size, noblock, &rc); lock_sock(sk); if (!skb) goto out; - skb->dev = llc->dev; + if (sock_flag(sk, SOCK_ZAPPED) || + llc->dev != dev || + hdrlen != llc_ui_header_len(sk, addr) || + hh_len != LL_RESERVED_SPACE(dev) || + size > READ_ONCE(dev->mtu)) + goto out; + skb->dev = dev; skb->protocol = llc_proto_type(addr->sllc_arphrd); - skb_reserve(skb, hdrlen); + skb_reserve(skb, hh_len + hdrlen); rc = memcpy_from_msg(skb_put(skb, copied), msg, copied); if (rc) goto out;