• Vegard Nossum's avatar
    ALSA: timer: fix NULL pointer dereference on memory allocation failure · 6138d59d
    Vegard Nossum authored
    [ Upstream commit 8ddc0563 ]
    
    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:[<ffffffff82c8ba07>]  [<ffffffff82c8ba07>] 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:
         [<ffffffff82c81ab1>] snd_timer_start1+0x331/0x670
         [<ffffffff82c85bfd>] snd_timer_start+0x5d/0xa0
         [<ffffffff82c8795e>] snd_timer_user_ioctl+0x88e/0x2830
         [<ffffffff8159f3a0>] ? __follow_pte.isra.49+0x430/0x430
         [<ffffffff82c870d0>] ? snd_timer_pause+0x80/0x80
         [<ffffffff815a26fa>] ? do_wp_page+0x3aa/0x1c90
         [<ffffffff8132762f>] ? put_prev_entity+0x108f/0x21a0
         [<ffffffff82c870d0>] ? snd_timer_pause+0x80/0x80
         [<ffffffff816b0733>] do_vfs_ioctl+0x193/0x1050
         [<ffffffff813510af>] ? cpuacct_account_field+0x12f/0x1a0
         [<ffffffff816b05a0>] ? ioctl_preallocate+0x200/0x200
         [<ffffffff81002f2f>] ? syscall_trace_enter+0x3cf/0xdb0
         [<ffffffff815045ba>] ? __context_tracking_exit.part.4+0x9a/0x1e0
         [<ffffffff81002b60>] ? exit_to_usermode_loop+0x190/0x190
         [<ffffffff82001a97>] ? check_preemption_disabled+0x37/0x1e0
         [<ffffffff81d93889>] ? security_file_ioctl+0x89/0xb0
         [<ffffffff816b167f>] SyS_ioctl+0x8f/0xc0
         [<ffffffff816b15f0>] ? do_vfs_ioctl+0x1050/0x1050
         [<ffffffff81005524>] do_syscall_64+0x1c4/0x4e0
         [<ffffffff83c32b2a>] 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  [<ffffffff82c8ba07>] snd_hrtimer_start+0x77/0x100
         RSP <ffff8801120c7a60>
        ---[ 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: default avatarVegard Nossum <vegard.nossum@oracle.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
    Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
    6138d59d
timer.c 53.6 KB