• Alexey Dobriyan's avatar
    proc: fix ->open'less usage due to ->proc_fops flip · 2d3a4e36
    Alexey Dobriyan authored
    Typical PDE creation code looks like:
    
    	pde = create_proc_entry("foo", 0, NULL);
    	if (pde)
    		pde->proc_fops = &foo_proc_fops;
    
    Notice that PDE is first created, only then ->proc_fops is set up to
    final value. This is a problem because right after creation
    a) PDE is fully visible in /proc , and
    b) ->proc_fops are proc_file_operations which do not have ->open callback. So, it's
       possible to ->read without ->open (see one class of oopses below).
    
    The fix is new API called proc_create() which makes sure ->proc_fops are
    set up before gluing PDE to main tree. Typical new code looks like:
    
    	pde = proc_create("foo", 0, NULL, &foo_proc_fops);
    	if (!pde)
    		return -ENOMEM;
    
    Fix most networking users for a start.
    
    In the long run, create_proc_entry() for regular files will go.
    
    BUG: unable to handle kernel NULL pointer dereference at virtual address 00000024
    printing eip: c1188c1b *pdpt = 000000002929e001 *pde = 0000000000000000
    Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC
    last sysfs file: /sys/block/sda/sda1/dev
    Modules linked in: foo af_packet ipv6 cpufreq_ondemand loop serio_raw psmouse k8temp hwmon sr_mod cdrom
    
    Pid: 24679, comm: cat Not tainted (2.6.24-rc3-mm1 #2)
    EIP: 0060:[<c1188c1b>] EFLAGS: 00210002 CPU: 0
    EIP is at mutex_lock_nested+0x75/0x25d
    EAX: 000006fe EBX: fffffffb ECX: 00001000 EDX: e9340570
    ESI: 00000020 EDI: 00200246 EBP: e9340570 ESP: e8ea1ef8
     DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
    Process cat (pid: 24679, ti=E8EA1000 task=E9340570 task.ti=E8EA1000)
    Stack: 00000000 c106f7ce e8ee05b4 00000000 00000001 458003d0 f6fb6f20 fffffffb
           00000000 c106f7aa 00001000 c106f7ce 08ae9000 f6db53f0 00000020 00200246
           00000000 00000002 00000000 00200246 00200246 e8ee05a0 fffffffb e8ee0550
    Call Trace:
     [<c106f7ce>] seq_read+0x24/0x28a
     [<c106f7aa>] seq_read+0x0/0x28a
     [<c106f7ce>] seq_read+0x24/0x28a
     [<c106f7aa>] seq_read+0x0/0x28a
     [<c10818b8>] proc_reg_read+0x60/0x73
     [<c1081858>] proc_reg_read+0x0/0x73
     [<c105a34f>] vfs_read+0x6c/0x8b
     [<c105a6f3>] sys_read+0x3c/0x63
     [<c10025f2>] sysenter_past_esp+0x5f/0xa5
     [<c10697a7>] destroy_inode+0x24/0x33
     =======================
    INFO: lockdep is turned off.
    Code: 75 21 68 e1 1a 19 c1 68 87 00 00 00 68 b8 e8 1f c1 68 25 73 1f c1 e8 84 06 e9 ff e8 52 b8 e7 ff 83 c4 10 9c 5f fa e8 28 89 ea ff <f0> fe 4e 04 79 0a f3 90 80 7e 04 00 7e f8 eb f0 39 76 34 74 33
    EIP: [<c1188c1b>] mutex_lock_nested+0x75/0x25d SS:ESP 0068:e8ea1ef8
    
    [akpm@linux-foundation.org: coding-style fixes]
    Signed-off-by: default avatarAlexey Dobriyan <adobriyan@sw.ru>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Cc: Oleg Nesterov <oleg@tv-sign.ru>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    2d3a4e36
root.c 5.17 KB