From 6b760bb2c63a9e322c0e4a0b5daf335ad93d5a33 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Mon, 29 Aug 2016 00:33:50 +0200 Subject: ALSA: timer: fix division by zero after SNDRV_TIMER_IOCTL_CONTINUE I got this: divide error: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 1327 Comm: a.out Not tainted 4.8.0-rc2+ #189 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014 task: ffff8801120a9580 task.stack: ffff8801120b0000 RIP: 0010:[] [] snd_hrtimer_callback+0x1da/0x3f0 RSP: 0018:ffff88011aa87da8 EFLAGS: 00010006 RAX: 0000000000004f76 RBX: ffff880112655e88 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff880112655ea0 RDI: 0000000000000001 RBP: ffff88011aa87e00 R08: ffff88013fff905c R09: ffff88013fff9048 R10: ffff88013fff9050 R11: 00000001050a7b8c R12: ffff880114778a00 R13: ffff880114778ab4 R14: ffff880114778b30 R15: 0000000000000000 FS: 00007f071647c700(0000) GS:ffff88011aa80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000603001 CR3: 0000000112021000 CR4: 00000000000006e0 Stack: 0000000000000000 ffff880114778ab8 ffff880112655ea0 0000000000004f76 ffff880112655ec8 ffff880112655e80 ffff880112655e88 ffff88011aa98fc0 00000000b97ccf2b dffffc0000000000 ffff88011aa98fc0 ffff88011aa87ef0 Call Trace: [] __hrtimer_run_queues+0x347/0xa00 [] ? snd_hrtimer_close+0x130/0x130 [] ? retrigger_next_event+0x1b0/0x1b0 [] ? hrtimer_interrupt+0x136/0x4b0 [] hrtimer_interrupt+0x1b0/0x4b0 [] local_apic_timer_interrupt+0x6e/0xf0 [] ? kvm_guest_apic_eoi_write+0x13/0xc0 [] smp_apic_timer_interrupt+0x76/0xa0 [] apic_timer_interrupt+0x8c/0xa0 [] ? _raw_spin_unlock_irqrestore+0x2c/0x60 [] snd_timer_start1+0xdd/0x670 [] snd_timer_continue+0x45/0x80 [] snd_timer_user_ioctl+0x1030/0x2830 [] ? __follow_pte.isra.49+0x430/0x430 [] ? snd_timer_pause+0x80/0x80 [] ? do_wp_page+0x3aa/0x1c90 [] ? handle_mm_fault+0xbc8/0x27f0 [] ? __pmd_alloc+0x370/0x370 [] ? snd_timer_pause+0x80/0x80 [] do_vfs_ioctl+0x193/0x1050 [] ? ioctl_preallocate+0x200/0x200 [] ? syscall_trace_enter+0x3cf/0xdb0 [] ? __context_tracking_exit.part.4+0x9a/0x1e0 [] ? exit_to_usermode_loop+0x190/0x190 [] ? check_preemption_disabled+0x37/0x1e0 [] ? security_file_ioctl+0x89/0xb0 [] SyS_ioctl+0x8f/0xc0 [] ? do_vfs_ioctl+0x1050/0x1050 [] do_syscall_64+0x1c4/0x4e0 [] entry_SYSCALL64_slow_path+0x25/0x25 Code: e8 fc 42 7b fe 8b 0d 06 8a 50 03 49 0f af cf 48 85 c9 0f 88 7c 01 00 00 48 89 4d a8 e8 e0 42 7b fe 48 8b 45 c0 48 8b 4d a8 48 99 <48> f7 f9 49 01 c7 e8 cb 42 7b fe 48 8b 55 d0 48 b8 00 00 00 00 RIP [] snd_hrtimer_callback+0x1da/0x3f0 RSP ---[ end trace 6aa380f756a21074 ]--- The problem happens when you call ioctl(SNDRV_TIMER_IOCTL_CONTINUE) on a completely new/unused timer -- it will have ->sticks == 0, which causes a divide by 0 in snd_hrtimer_callback(). Signed-off-by: Vegard Nossum Cc: Signed-off-by: Takashi Iwai --- sound/core/timer.c | 1 + 1 file changed, 1 insertion(+) (limited to 'sound/core/timer.c') diff --git a/sound/core/timer.c b/sound/core/timer.c index 9a6157ea6881..00618703c58f 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -813,6 +813,7 @@ int snd_timer_new(struct snd_card *card, char *id, struct snd_timer_id *tid, timer->tmr_subdevice = tid->subdevice; if (id) strlcpy(timer->id, id, sizeof(timer->id)); + timer->sticks = 1; INIT_LIST_HEAD(&timer->device_list); INIT_LIST_HEAD(&timer->open_list_head); INIT_LIST_HEAD(&timer->active_list_head); -- cgit v1.2.3 From 8ddc05638ee42b18ba4fe99b5fb647fa3ad20456 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Mon, 29 Aug 2016 00:33:51 +0200 Subject: ALSA: timer: fix NULL pointer dereference on memory allocation failure I hit this with syzkaller: kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 1327 Comm: a.out Not tainted 4.8.0-rc2+ #190 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014 task: ffff88011278d600 task.stack: ffff8801120c0000 RIP: 0010:[] [] snd_hrtimer_start+0x77/0x100 RSP: 0018:ffff8801120c7a60 EFLAGS: 00010006 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000007 RDX: 0000000000000009 RSI: 1ffff10023483091 RDI: 0000000000000048 RBP: ffff8801120c7a78 R08: ffff88011a5cf768 R09: ffff88011a5ba790 R10: 0000000000000002 R11: ffffed00234b9ef1 R12: ffff880114843980 R13: ffffffff84213c00 R14: ffff880114843ab0 R15: 0000000000000286 FS: 00007f72958f3700(0000) GS:ffff88011aa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000603001 CR3: 00000001126ab000 CR4: 00000000000006f0 Stack: ffff880114843980 ffff880111eb2dc0 ffff880114843a34 ffff8801120c7ad0 ffffffff82c81ab1 0000000000000000 ffffffff842138e0 0000000100000000 ffff880111eb2dd0 ffff880111eb2dc0 0000000000000001 ffff880111eb2dc0 Call Trace: [] snd_timer_start1+0x331/0x670 [] snd_timer_start+0x5d/0xa0 [] snd_timer_user_ioctl+0x88e/0x2830 [] ? __follow_pte.isra.49+0x430/0x430 [] ? snd_timer_pause+0x80/0x80 [] ? do_wp_page+0x3aa/0x1c90 [] ? put_prev_entity+0x108f/0x21a0 [] ? snd_timer_pause+0x80/0x80 [] do_vfs_ioctl+0x193/0x1050 [] ? cpuacct_account_field+0x12f/0x1a0 [] ? ioctl_preallocate+0x200/0x200 [] ? syscall_trace_enter+0x3cf/0xdb0 [] ? __context_tracking_exit.part.4+0x9a/0x1e0 [] ? exit_to_usermode_loop+0x190/0x190 [] ? check_preemption_disabled+0x37/0x1e0 [] ? security_file_ioctl+0x89/0xb0 [] SyS_ioctl+0x8f/0xc0 [] ? do_vfs_ioctl+0x1050/0x1050 [] do_syscall_64+0x1c4/0x4e0 [] entry_SYSCALL64_slow_path+0x25/0x25 Code: c7 c7 c4 b9 c8 82 48 89 d9 4c 89 ee e8 63 88 7f fe e8 7e 46 7b fe 48 8d 7b 48 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 04 84 c0 7e 65 80 7b 48 00 74 0e e8 52 46 RIP [] snd_hrtimer_start+0x77/0x100 RSP ---[ end trace 5955b08db7f2b029 ]--- This can happen if snd_hrtimer_open() fails to allocate memory and returns an error, which is currently not checked by snd_timer_open(): ioctl(SNDRV_TIMER_IOCTL_SELECT) - snd_timer_user_tselect() - snd_timer_close() - snd_hrtimer_close() - (struct snd_timer *) t->private_data = NULL - snd_timer_open() - snd_hrtimer_open() - kzalloc() fails; t->private_data is still NULL ioctl(SNDRV_TIMER_IOCTL_START) - snd_timer_user_start() - snd_timer_start() - snd_timer_start1() - snd_hrtimer_start() - t->private_data == NULL // boom Signed-off-by: Vegard Nossum Cc: Signed-off-by: Takashi Iwai --- sound/core/timer.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'sound/core/timer.c') diff --git a/sound/core/timer.c b/sound/core/timer.c index 00618703c58f..2d6e3e76ddf5 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -294,8 +294,21 @@ int snd_timer_open(struct snd_timer_instance **ti, get_device(&timer->card->card_dev); timeri->slave_class = tid->dev_sclass; timeri->slave_id = slave_id; - if (list_empty(&timer->open_list_head) && timer->hw.open) - timer->hw.open(timer); + + if (list_empty(&timer->open_list_head) && timer->hw.open) { + int err = timer->hw.open(timer); + if (err) { + kfree(timeri->owner); + kfree(timeri); + + if (timer->card) + put_device(&timer->card->card_dev); + module_put(timer->module); + mutex_unlock(®ister_mutex); + return err; + } + } + list_add_tail(&timeri->open_list, &timer->open_list_head); snd_timer_check_master(timeri); mutex_unlock(®ister_mutex); -- cgit v1.2.3 From 11749e086b2766cccf6217a527ef5c5604ba069c Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Sun, 28 Aug 2016 10:13:07 +0200 Subject: ALSA: timer: fix NULL pointer dereference in read()/ioctl() race I got this with syzkaller: ================================================================== BUG: KASAN: null-ptr-deref on address 0000000000000020 Read of size 32 by task syz-executor/22519 CPU: 1 PID: 22519 Comm: syz-executor Not tainted 4.8.0-rc2+ #169 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2 014 0000000000000001 ffff880111a17a00 ffffffff81f9f141 ffff880111a17a90 ffff880111a17c50 ffff880114584a58 ffff880114584a10 ffff880111a17a80 ffffffff8161fe3f ffff880100000000 ffff880118d74a48 ffff880118d74a68 Call Trace: [] dump_stack+0x83/0xb2 [] kasan_report_error+0x41f/0x4c0 [] kasan_report+0x34/0x40 [] ? snd_timer_user_read+0x554/0x790 [] check_memory_region+0x13e/0x1a0 [] kasan_check_read+0x11/0x20 [] snd_timer_user_read+0x554/0x790 [] ? snd_timer_user_info_compat.isra.5+0x2b0/0x2b0 [] ? proc_fault_inject_write+0x1c1/0x250 [] ? next_tgid+0x2a0/0x2a0 [] ? do_group_exit+0x108/0x330 [] ? fsnotify+0x72a/0xca0 [] __vfs_read+0x10e/0x550 [] ? snd_timer_user_info_compat.isra.5+0x2b0/0x2b0 [] ? do_sendfile+0xc50/0xc50 [] ? __fsnotify_update_child_dentry_flags+0x60/0x60 [] ? kcov_ioctl+0x56/0x190 [] ? common_file_perm+0x2e2/0x380 [] ? __fsnotify_parent+0x5e/0x2b0 [] ? security_file_permission+0x86/0x1e0 [] ? rw_verify_area+0xe5/0x2b0 [] vfs_read+0x115/0x330 [] SyS_read+0xd1/0x1a0 [] ? vfs_write+0x4b0/0x4b0 [] ? __this_cpu_preempt_check+0x1c/0x20 [] ? __context_tracking_exit.part.4+0x3a/0x1e0 [] ? vfs_write+0x4b0/0x4b0 [] do_syscall_64+0x1c4/0x4e0 [] ? syscall_return_slowpath+0x16c/0x1d0 [] entry_SYSCALL64_slow_path+0x25/0x25 ================================================================== There are a couple of problems that I can see: - ioctl(SNDRV_TIMER_IOCTL_SELECT), which potentially sets tu->queue/tu->tqueue to NULL on memory allocation failure, so read() would get a NULL pointer dereference like the above splat - the same ioctl() can free tu->queue/to->tqueue which means read() could potentially see (and dereference) the freed pointer We can fix both by taking the ioctl_lock mutex when dereferencing ->queue/->tqueue, since that's always held over all the ioctl() code. Just looking at the code I find it likely that there are more problems here such as tu->qhead pointing outside the buffer if the size is changed concurrently using SNDRV_TIMER_IOCTL_PARAMS. Signed-off-by: Vegard Nossum Cc: Signed-off-by: Takashi Iwai --- sound/core/timer.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'sound/core/timer.c') diff --git a/sound/core/timer.c b/sound/core/timer.c index 2d6e3e76ddf5..2706061fc1ea 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1972,6 +1972,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, tu->qused--; spin_unlock_irq(&tu->qlock); + mutex_lock(&tu->ioctl_lock); if (tu->tread) { if (copy_to_user(buffer, &tu->tqueue[qhead], sizeof(struct snd_timer_tread))) @@ -1981,6 +1982,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, sizeof(struct snd_timer_read))) err = -EFAULT; } + mutex_unlock(&tu->ioctl_lock); spin_lock_irq(&tu->qlock); if (err < 0) -- cgit v1.2.3 From 9f8a7658bcafb2a7853f7a2eae8a94e87e6e695b Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Wed, 7 Sep 2016 15:45:31 +0200 Subject: ALSA: timer: Fix zero-division by continue of uninitialized instance When a user timer instance is continued without the explicit start beforehand, the system gets eventually zero-division error like: divide error: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN CPU: 1 PID: 27320 Comm: syz-executor Not tainted 4.8.0-rc3-next-20160825+ #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff88003c9b2280 task.stack: ffff880027280000 RIP: 0010:[] [< inline >] ktime_divns include/linux/ktime.h:195 RIP: 0010:[] [] snd_hrtimer_callback+0x1bc/0x3c0 sound/core/hrtimer.c:62 Call Trace: [< inline >] __run_hrtimer kernel/time/hrtimer.c:1238 [] __hrtimer_run_queues+0x325/0xe70 kernel/time/hrtimer.c:1302 [] hrtimer_interrupt+0x18b/0x420 kernel/time/hrtimer.c:1336 [] local_apic_timer_interrupt+0x6f/0xe0 arch/x86/kernel/apic/apic.c:933 [] smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:957 [] apic_timer_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:487 ..... Although a similar issue was spotted and a fix patch was merged in commit [6b760bb2c63a: ALSA: timer: fix division by zero after SNDRV_TIMER_IOCTL_CONTINUE], it seems covering only a part of iceberg. In this patch, we fix the issue a bit more drastically. Basically the continue of an uninitialized timer is supposed to be a fresh start, so we do it for user timers. For the direct snd_timer_continue() call, there is no way to pass the initial tick value, so we kick out for the uninitialized case. Reported-by: Dmitry Vyukov Cc: Signed-off-by: Takashi Iwai --- sound/core/timer.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'sound/core/timer.c') diff --git a/sound/core/timer.c b/sound/core/timer.c index 2706061fc1ea..fc144f43faa6 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -35,6 +35,9 @@ #include #include +/* internal flags */ +#define SNDRV_TIMER_IFLG_PAUSED 0x00010000 + #if IS_ENABLED(CONFIG_SND_HRTIMER) #define DEFAULT_TIMER_LIMIT 4 #else @@ -539,6 +542,10 @@ static int snd_timer_stop1(struct snd_timer_instance *timeri, bool stop) } } timeri->flags &= ~(SNDRV_TIMER_IFLG_RUNNING | SNDRV_TIMER_IFLG_START); + if (stop) + timeri->flags &= ~SNDRV_TIMER_IFLG_PAUSED; + else + timeri->flags |= SNDRV_TIMER_IFLG_PAUSED; snd_timer_notify1(timeri, stop ? SNDRV_TIMER_EVENT_STOP : SNDRV_TIMER_EVENT_CONTINUE); unlock: @@ -600,6 +607,10 @@ int snd_timer_stop(struct snd_timer_instance *timeri) */ int snd_timer_continue(struct snd_timer_instance *timeri) { + /* timer can continue only after pause */ + if (!(timeri->flags & SNDRV_TIMER_IFLG_PAUSED)) + return -EINVAL; + if (timeri->flags & SNDRV_TIMER_IFLG_SLAVE) return snd_timer_start_slave(timeri, false); else @@ -1831,6 +1842,9 @@ static int snd_timer_user_continue(struct file *file) tu = file->private_data; if (!tu->timeri) return -EBADFD; + /* start timer instead of continue if it's not used before */ + if (!(tu->timeri->flags & SNDRV_TIMER_IFLG_PAUSED)) + return snd_timer_user_start(file); tu->timeri->lost = 0; return (err = snd_timer_continue(tu->timeri)) < 0 ? err : 0; } -- cgit v1.2.3