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phonet: Check input from user before allocating
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A phonet packet is limited to USHRT_MAX bytes, this is never checked during
tx which means that the user can specify any size he wishes, and the kernel
will attempt to allocate that size.

In the good case, it'll lead to the following warning, but it may also cause
the kernel to kick in the OOM and kill a random task on the server.

[ 8921.744094] WARNING: at mm/page_alloc.c:2255 __alloc_pages_slowpath+0x65/0x730()
[ 8921.749770] Pid: 5081, comm: trinity Tainted: G        W    3.4.0-rc1-next-20120402-sasha torvalds#46
[ 8921.756672] Call Trace:
[ 8921.758185]  [<ffffffff810b2ba7>] warn_slowpath_common+0x87/0xb0
[ 8921.762868]  [<ffffffff810b2be5>] warn_slowpath_null+0x15/0x20
[ 8921.765399]  [<ffffffff8117eae5>] __alloc_pages_slowpath+0x65/0x730
[ 8921.769226]  [<ffffffff81179c8a>] ? zone_watermark_ok+0x1a/0x20
[ 8921.771686]  [<ffffffff8117d045>] ? get_page_from_freelist+0x625/0x660
[ 8921.773919]  [<ffffffff8117f3a8>] __alloc_pages_nodemask+0x1f8/0x240
[ 8921.776248]  [<ffffffff811c03e0>] kmalloc_large_node+0x70/0xc0
[ 8921.778294]  [<ffffffff811c4bd4>] __kmalloc_node_track_caller+0x34/0x1c0
[ 8921.780847]  [<ffffffff821b0e3c>] ? sock_alloc_send_pskb+0xbc/0x260
[ 8921.783179]  [<ffffffff821b3c65>] __alloc_skb+0x75/0x170
[ 8921.784971]  [<ffffffff821b0e3c>] sock_alloc_send_pskb+0xbc/0x260
[ 8921.787111]  [<ffffffff821b002e>] ? release_sock+0x7e/0x90
[ 8921.788973]  [<ffffffff821b0ff0>] sock_alloc_send_skb+0x10/0x20
[ 8921.791052]  [<ffffffff824cfc20>] pep_sendmsg+0x60/0x380
[ 8921.792931]  [<ffffffff824cb4a6>] ? pn_socket_bind+0x156/0x180
[ 8921.794917]  [<ffffffff824cb50f>] ? pn_socket_autobind+0x3f/0x90
[ 8921.797053]  [<ffffffff824cb63f>] pn_socket_sendmsg+0x4f/0x70
[ 8921.798992]  [<ffffffff821ab8e7>] sock_aio_write+0x187/0x1b0
[ 8921.801395]  [<ffffffff810e325e>] ? sub_preempt_count+0xae/0xf0
[ 8921.803501]  [<ffffffff8111842c>] ? __lock_acquire+0x42c/0x4b0
[ 8921.805505]  [<ffffffff821ab760>] ? __sock_recv_ts_and_drops+0x140/0x140
[ 8921.807860]  [<ffffffff811e07cc>] do_sync_readv_writev+0xbc/0x110
[ 8921.809986]  [<ffffffff811958e7>] ? might_fault+0x97/0xa0
[ 8921.811998]  [<ffffffff817bd99e>] ? security_file_permission+0x1e/0x90
[ 8921.814595]  [<ffffffff811e17e2>] do_readv_writev+0xe2/0x1e0
[ 8921.816702]  [<ffffffff810b8dac>] ? do_setitimer+0x1ac/0x200
[ 8921.818819]  [<ffffffff810e2ec1>] ? get_parent_ip+0x11/0x50
[ 8921.820863]  [<ffffffff810e325e>] ? sub_preempt_count+0xae/0xf0
[ 8921.823318]  [<ffffffff811e1926>] vfs_writev+0x46/0x60
[ 8921.825219]  [<ffffffff811e1a3f>] sys_writev+0x4f/0xb0
[ 8921.827127]  [<ffffffff82658039>] system_call_fastpath+0x16/0x1b
[ 8921.829384] ---[ end trace dffe390f30db9eb7 ]---

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Acked-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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sashalevin authored and davem330 committed Apr 5, 2012
1 parent 35f9c09 commit bcf1b70
Showing 1 changed file with 3 additions and 0 deletions.
3 changes: 3 additions & 0 deletions net/phonet/pep.c
Original file line number Diff line number Diff line change
Expand Up @@ -1130,6 +1130,9 @@ static int pep_sendmsg(struct kiocb *iocb, struct sock *sk,
int flags = msg->msg_flags;
int err, done;

if (len > USHRT_MAX)
return -EMSGSIZE;

if ((msg->msg_flags & ~(MSG_DONTWAIT|MSG_EOR|MSG_NOSIGNAL|
MSG_CMSG_COMPAT)) ||
!(msg->msg_flags & MSG_EOR))
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