[BUG] 2.6.25-rcX NULL Pointer when adding a mutex_waiter
From: Bongani Hlope
Date: Tue Feb 26 2008 - 18:28:15 EST
Hi
I've been trying to figure out what causes [BUG 10027] on bugzilla , and I'm
stuck. The 2.6.24 kernel works fine, the bttv drivers have been ported to V4L
version 2 API, so bisecting doesn't work that well.
My analysis of the bug is as follows:
linux/driver/media/video/bt8x/bttv-driver.c:4284
mutex_init(&btv->lock); in __devinit bttv_probe()
The printk's before and after this statement are printed, which implies that
the mutex_init was successfull. This driver uses locks and unlocks this
mutex in a lot of places and driving the TV part of the card works fine.
linux/kernel/mutex.c:47
INIT_LIST_HEAD(&lock->wait_list); in __mutex_init, which is called by
mutex_init. This initializes the list of waiters for this mutex
the radio_g_tuner causes the following call chain:
mutex_lock -> __mutex_lock_slowpath -> __mutex_lock_common,
which does this:
/* add waiting tasks to the end of the waitqueue (FIFO): */
list_add_tail(&waiter.list, &lock->wait_list);
waiter.task = task;
which causes __list_add to fail:
Code disassembled:
0x4005c0 <array>: mov %edi,%ebx
0x4005c2 <array+2>: mov %r12,%rdi
0x4005c5 <array+5>: sub $0x20,%rsp
0x4005c9 <array+9>: mov %gs:0x0,%r14
0x4005d2 <array+18>: callq 0x4017f0
0x4005d7 <array+23>: lea 0x8(%rbx),%rax
0x4005db <array+27>: lea 0xffffffffffffffc0(%rbp),%rdx
0x4005df <array+31>: mov 0x8(%rax),%rcx
0x4005e3 <array+35>: mov %rax,0xffffffffffffffc0(%rbp)
0x4005e7 <array+39>: mov %rdx,0x8(%rax)
0x4005eb <array+43>: mov %rdx,(%rcx) <============= Here
0x4005ee <array+46>: or $0xffffffffffffffff,%rdx
0x4005f2 <array+50>: mov %rcx,0xffffffffffffffc8(%rbp)
0x4005f6 <array+54>: mov %r14,0xffffffffffffffd0(%rbp)
0x4005fa <array+58>: mov %rdx,%rax
0x4005fd <array+61>: xchg %eax,(%rbx)
0x4005ff <array+63>: incl (%rax)
0x400601: and $0xa70,%eax
0x400606: add %al,(%rax)
0x400608: add %ebx,(%rbx)
kernel/mutext.c dissamble:
__mutex_lock_slowpath:
pushq %rbp #
movq %rsp, %rbp #,
pushq %r14 #
pushq %r13 #
pushq %r12 #
leaq 4(%rdi), %r12 #, D.13845
pushq %rbx #
movq %rdi, %rbx # lock_count, lock
movq %r12, %rdi # D.13845, D.13845
subq $32, %rsp #,
#APP
movq %gs:0,%r14 #, tsk
#NO_APP
call _spin_lock #
leaq 8(%rbx), %rax #, next
leaq -64(%rbp), %rdx #, tmp81
movq 8(%rax), %rcx # <variable>.prev, prev
movq %rax, -64(%rbp) # next, waiter.list.next
movq %rdx, 8(%rax) # tmp81, <variable>.prev
movq %rdx, (%rcx) # tmp81, <variable>.next <========= Here
orq $-1, %rdx #, tmp83
movq %rcx, -56(%rbp) # prev, waiter.list.prev
movq %r14, -48(%rbp) # tsk, waiter.task
movq %rdx, %rax # tmp83, x
the oops
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
IP: [<ffffffff8045723d>] __mutex_lock_slowpath+0x3b/0xb2
PGD 67671067 PUD 63f47067 PMD 0
Oops: 0002 [1] PREEMPT SMP
CPU 0
Modules linked in: snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq
binfmt_misc loop nls_cp437 vfat fat nls_iso8859_1 ntfs dm_mod thermal
processor fan container button pcspkr snd_pcm_oss snd_mixer_oss tuner tea5767
tda8290 tuner_xc2028 tda9887 tuner_simple mt20xx tea5761 snd_emu10k1
snd_rawmidi bttv snd_ac97_codec videodev ac97_bus v4l1_compat snd_pcm
ir_common firewire_ohci firewire_core snd_seq_device compat_ioctl32 snd_timer
uhci_hcd ehci_hcd v4l2_common ide_cd_mod crc_itu_t snd_page_alloc usbcore
videobuf_dma_sg snd_util_mem videobuf_core ohci1394 btcx_risc i2c_viapro
sr_mod snd_hwdep ieee1394 emu10k1_gp snd tg3 cdrom tveeprom gameport sg evdev
soundcore
Pid: 7197, comm: radio Tainted: G M 2.6.25-rc1 #20
RIP: 0010:[<ffffffff8045723d>] [<ffffffff8045723d>]
__mutex_lock_slowpath+0x3b/0xb2
RSP: 0018:ffff81007df515e8 EFLAGS: 00010246
RAX: ffff81007f13ef10 RBX: ffff81007f13ef08 RCX: 0000000000000000
RDX: ffff81007df515e8 RSI: ffffffff88184050 RDI: ffff81007f13ef0c
RBP: ffff81007df51628 R08: 0000000000000004 R09: ffff81007df51aa8
R10: ffff81007e680a40 R11: 0000000000000202 R12: ffff81007f13ef0c
R13: ffff81007f13ef08 R14: ffff810063cfc040 R15: ffffffff88184050
FS: 00007fa8d92ba6f0(0000) GS:ffffffff805b2000(0000) knlGS:00000000f61fb980
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000676dc000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process radio (pid: 7197, threadinfo ffff81007df50000, task ffff810063cfc040)
Stack: ffff81007f13ef10 0005049900000000 018060f7018060fa 0000000000000024
ffff81007df51aa8 ffff81007f13e800 ffff81007f13ef08 ffff81007e0e5800
ffff81007df51638 ffffffff80457083 ffff81007df51668 ffffffff88162f2f
Call Trace:
[<ffffffff80457083>]
[<ffffffff88162f2f>] :bttv:radio_g_tuner+0x40/0xa6
[<ffffffff8813df7d>] :videodev:__video_do_ioctl+0x2a6e/0x2e25
[<ffffffff8813503c>] :v4l1_compat:v4l_compat_translate_ioctl+0xea9/0x1af5
[<ffffffff8813b50f>] ? :videodev:__video_do_ioctl+0x0/0x2e25
[<ffffffff80301f4b>] ? blk_recount_segments+0x3e/0x62
[<ffffffff80260f7b>] ? mempool_alloc_slab+0x11/0x13
[<ffffffff80261085>] ? mempool_alloc+0x48/0xf9
[<ffffffff802e3369>] ? ext3_get_acl+0x87/0x332
[<ffffffff80296c65>] ? __d_lookup+0x125/0x137
[<ffffffff8028d54f>] ? do_lookup+0x63/0x1b1
[<ffffffff802961c3>] ? dput+0x22/0x120
[<ffffffff8028f6a6>] ? __link_path_walk+0xbbd/0xd1b
[<ffffffff802e3369>] ? ext3_get_acl+0x87/0x332
[<ffffffff802115d1>] ? native_read_tsc+0x11/0x22
[<ffffffff80310e1b>] ? __delay+0x27/0x59
last message repeated 2 times
[<ffffffff80310ecf>] ? __udelay+0x40/0x42
[<ffffffff803c0950>] ? i2c_stop+0x47/0x4b
[<ffffffff803c1117>] ? bit_xfer+0x412/0x423
[<ffffffff803bef99>] ? i2c_transfer+0x79/0x85
[<ffffffff881cc31c>] ? :tuner_simple:simple_set_params+0x2bd/0xc1c
[<ffffffff80284607>] ? get_unused_fd_flags+0x10d/0x11c
[<ffffffff8029965b>] ? touch_atime+0xe3/0xec
[<ffffffff8029b113>] ? mntput_no_expire+0x20/0x8f
[<ffffffff881e3447>] ? :tuner:fe_set_params+0x46/0x48
[<ffffffff881e285c>] ? :tuner:set_radio_freq+0x159/0x162
[<ffffffff80449dfb>] ? klist_dec_and_del+0x14/0x16
[<ffffffff80449e68>] ? klist_next+0x6b/0x8a
[<ffffffff803c075a>] ? i2c_cmd+0x0/0x3e
[<ffffffff8037c62f>] ? device_for_each_child+0x4c/0x5c
[<ffffffff8813b648>] :videodev:__video_do_ioctl+0x139/0x2e25
[<ffffffff88168b56>] ? :bttv:bttv_call_i2c_clients+0x16/0x18
[<ffffffff88161ed2>] ? :bttv:audio_mux+0x105/0x1b5
[<ffffffff80260d39>] ? filemap_fault+0x1fe/0x371
[<ffffffff8813e6d4>] :videodev:video_ioctl2+0x1b8/0x259
[<ffffffff8026dc63>] ? handle_mm_fault+0x341/0x697
[<ffffffff80291c36>] vfs_ioctl+0x5e/0x77
[<ffffffff80291e9c>] do_vfs_ioctl+0x24d/0x262
[<ffffffff8045a9d7>] ? do_page_fault+0x434/0x7aa
[<ffffffff80291ef3>] sys_ioctl+0x42/0x67
[<ffffffff8020b36b>] system_call_after_swapgs+0x7b/0x80
Feb 15 08:42:03 bongani64 kernel:
Feb 15 08:42:03 bongani64 kernel:
Code: 89 fb 4c 89 e7 48 83 ec 20 65 4c 8b 34 25 00 00 00 00 e8 19 12 00 00 48
8d 43 08 48 8d 55 c0 48 8b 48 08 48 89 45 c0 48 89 50 08 <48> 89 11 48 83 ca
ff 48 89 4d c8 4c 89 75 d0 48 89 d0 87 03 ff
RIP [<ffffffff8045723d>] __mutex_lock_slowpath+0x3b/0xb2
RSP <ffff81007df515e8>
CR2: 0000000000000000
---[ end trace fdf145f4fc51dccd ]---
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