4.4-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 2c5d5b13c6eb79f5677e206b8aad59b3a2097f60 ]
syzbot loves to set very small mtu on devices, since it brings joy. We must make llc_ui_sendmsg() fool proof.
usercopy: Kernel memory overwrite attempt detected to wrapped address (offset 0, size 18446612139802320068)!
kernel BUG at mm/usercopy.c:100! invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 0 PID: 17464 Comm: syz-executor1 Not tainted 4.17.0-rc3+ #36 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:usercopy_abort+0xbb/0xbd mm/usercopy.c:88 RSP: 0018:ffff8801868bf800 EFLAGS: 00010282 RAX: 000000000000006c RBX: ffffffff87d2fb00 RCX: 0000000000000000 RDX: 000000000000006c RSI: ffffffff81610731 RDI: ffffed0030d17ef6 RBP: ffff8801868bf858 R08: ffff88018daa4200 R09: ffffed003b5c4fb0 R10: ffffed003b5c4fb0 R11: ffff8801dae27d87 R12: ffffffff87d2f8e0 R13: ffffffff87d2f7a0 R14: ffffffff87d2f7a0 R15: ffffffff87d2f7a0 FS: 00007f56a14ac700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2bc21000 CR3: 00000001abeb1000 CR4: 00000000001426f0 DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000030602 Call Trace: check_bogus_address mm/usercopy.c:153 [inline] __check_object_size+0x5d9/0x5d9 mm/usercopy.c:256 check_object_size include/linux/thread_info.h:108 [inline] check_copy_size include/linux/thread_info.h:139 [inline] copy_from_iter_full include/linux/uio.h:121 [inline] memcpy_from_msg include/linux/skbuff.h:3305 [inline] llc_ui_sendmsg+0x4b1/0x1530 net/llc/af_llc.c:941 sock_sendmsg_nosec net/socket.c:629 [inline] sock_sendmsg+0xd5/0x120 net/socket.c:639 __sys_sendto+0x3d7/0x670 net/socket.c:1789 __do_sys_sendto net/socket.c:1801 [inline] __se_sys_sendto net/socket.c:1797 [inline] __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1797 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x455979 RSP: 002b:00007f56a14abc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f56a14ac6d4 RCX: 0000000000455979 RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000018 RBP: 000000000072bea0 R08: 00000000200012c0 R09: 0000000000000010 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000548 R14: 00000000006fbf60 R15: 0000000000000000 Code: 55 c0 e8 c0 55 bb ff ff 75 c8 48 8b 55 c0 4d 89 f9 ff 75 d0 4d 89 e8 48 89 d9 4c 89 e6 41 56 48 c7 c7 80 fa d2 87 e8 a0 0b a3 ff <0f> 0b e8 95 55 bb ff e8 c0 a8 f7 ff 8b 95 14 ff ff ff 4d 89 e8 RIP: usercopy_abort+0xbb/0xbd mm/usercopy.c:88 RSP: ffff8801868bf800
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/llc/af_llc.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/net/llc/af_llc.c +++ b/net/llc/af_llc.c @@ -926,6 +926,9 @@ static int llc_ui_sendmsg(struct socket if (size > llc->dev->mtu) size = llc->dev->mtu; copied = size - hdrlen; + rc = -EINVAL; + if (copied < 0) + goto release; release_sock(sk); skb = sock_alloc_send_skb(sk, size, noblock, &rc); lock_sock(sk);