[BUG] Null pointer deref with hrtimer_try_to_cancel()

[Eric Sesterhenn <snakebyte@gmx.de>]

hi,

I was running the strace-test from ltp 20081130 with 2.6.28-rc9, when i got the following bug
(I can reproduce the bug by simply running the testcase timer_create04)

[ 2460.441441] BUG: unable to handle kernel NULL pointer dereference at
00000003
[ 2460.441749] IP: [<c02a78c1>] _raw_spin_lock+0x11/0x110
[ 2460.442012] *pde = 00000000 
[ 2460.442161] Oops: 0000 [#2] DEBUG_PAGEALLOC
[ 2460.442420] last sysfs file: /sys/block/sda/size
[ 2460.442541] Modules linked in: sctp nfsd auth_rpcgss exportfs nfs
lockd nfs_acl sunrpc ipv6 fuse unix
[ 2460.443471] 
[ 2460.443628] Pid: 14406, comm: timer_create04 Tainted: G      D W
(2.6.28-rc9 #71) 
[ 2460.443811] EIP: 0060:[<c02a78c1>] EFLAGS: 00010096 CPU: 0
[ 2460.443941] EIP is at _raw_spin_lock+0x11/0x110
[ 2460.444044] EAX: ffffffff EBX: ffffffff ECX: 00000000 EDX: 00000000
[ 2460.444044] ESI: 00000096 EDI: c08337ec EBP: c8fc7ee0 ESP: c8fc7eb8
[ 2460.444044]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
[ 2460.444044] Process timer_create04 (pid: 14406, ti=c8fc7000
task=c8db5710 task.ti=c8fc7000)
[ 2460.444044] Stack:
[ 2460.444044]  00000046 00000000 00000002 00000001 00000000 c0141070
0000000f ffffffff
[ 2460.444044]  00000096 c08337ec c8fc7f00 c05ac067 00000000 00000002
00000000 c0141070
[ 2460.444044]  ffffffff c1956aa4 c8fc7f1c c0141070 00000002 00000000
c1956a60 c1956a68
[ 2460.444044] Call Trace:
[ 2460.444044]  [<c0141070>] ? hrtimer_try_to_cancel+0x20/0x90
[ 2460.444044]  [<c05ac067>] ? _spin_lock_irqsave+0x47/0x60
[ 2460.444044]  [<c0141070>] ? hrtimer_try_to_cancel+0x20/0x90
[ 2460.444044]  [<c0141070>] ? hrtimer_try_to_cancel+0x20/0x90
[ 2460.444044]  [<c013cf94>] ? exit_itimers+0x94/0xf0
[ 2460.444044]  [<c012cab2>] ? do_exit+0x602/0x810
[ 2460.444044]  [<c05abe5d>] ? _spin_unlock+0x1d/0x20
[ 2460.444044]  [<c01a245e>] ? vfs_write+0xfe/0x160
[ 2460.444044]  [<c0319090>] ? tty_write+0x0/0x1f0
[ 2460.444044]  [<c012ccef>] ? do_group_exit+0x2f/0x90
[ 2460.444044]  [<c012cd63>] ? sys_exit_group+0x13/0x20
[ 2460.444044]  [<c01035a9>] ? sysenter_do_call+0x12/0x31
[ 2460.444044] Code: 00 a1 00 c0 82 c0 89 41 0c 89 d8 5b 5d c3 8d b6 00
00 00 00 8d bf 00 00 00 00 55 89 e5 83 ec 28 89 5d f4 89 c3 89 75 f8 89
7d fc <81> 78 04 ad 4e ad de 74 0a ba 77 3f 79 c0 e8 2c fe ff ff a1 00 
[ 2460.444044] EIP: [<c02a78c1>] _raw_spin_lock+0x11/0x110 SS:ESP
0068:c8fc7eb8
[ 2460.444044] ---[ end trace 85ae5af0da78d5d7 ]---
[ 2460.444044] Fixing recursive fault but reboot is needed!



(gdb) l *(_raw_spin_lock+0x11)
0xc02a78c1 is in _raw_spin_lock (lib/spinlock_debug.c:78).
73	#define SPIN_BUG_ON(cond, lock, msg) if (unlikely(cond))
spin_bug(lock, msg)
74	
75	static inline void
76	debug_spin_lock_before(spinlock_t *lock)
77	{
78		SPIN_BUG_ON(lock->magic != SPINLOCK_MAGIC, lock, "bad
magic");
79		SPIN_BUG_ON(lock->owner == current, lock, "recursion");
80		SPIN_BUG_ON(lock->owner_cpu == raw_smp_processor_id(),
81								lock,
"cpu recursion");
82	}
(gdb) q

(gdb) l *(hrtimer_try_to_cancel+0x20)
0xc0141070 is in hrtimer_try_to_cancel (kernel/hrtimer.c:234).
229	static inline struct hrtimer_clock_base *
230	lock_hrtimer_base(const struct hrtimer *timer, unsigned long
*flags)
231	{
232		struct hrtimer_clock_base *base = timer->base;
233	
234		spin_lock_irqsave(&base->cpu_base->lock, *flags);
235	
236		return base;
237	}
238	
(gdb) 

The testcase aborts in pass number 6:

root@computer-desktop:~/testing/ltp-full-20081130/tools/strace_test#
./timer_create04 
timer_create04    1  FAIL  :  timer_create(2) failed to produce expected
error; 22 , errno : EINVAL and got 0
timer_create04    2  PASS  :  timer_create(2) expected failure; Got
errno - EINVAL : Invalid parameter
timer_create04    3  PASS  :  timer_create(2) expected failure; Got
errno - EFAULT : Bad address
timer_create04    4  PASS  :  timer_create(2) expected failure; Got
errno - EFAULT : Bad address
timer_create04    5  PASS  :  timer_create(2) expected failure; Got
errno - EFAULT : Bad address
timer_create04    6  PASS  :  timer_create(2) expected failure; Got
errno - EFAULT : Bad address

Greetings, Eric