linux.git/fs/proc/inode.c, branch v2.6.24

proc: fix proc_dir_entry refcounting

2007-12-05T17:21:20+00:00

Creating PDEs with refcount 0 and "deleted" flag has problems (see below).
Switch to usual scheme:
* PDE is created with refcount 1
* every de_get does +1
* every de_put() and remove_proc_entry() do -1
* once refcount reaches 0, PDE is freed.

This elegantly fixes at least two following races (both observed) without
introducing new locks, without abusing old locks, without spreading
lock_kernel():

1) PDE leak

remove_proc_entry			de_put
-----------------			------
			[refcnt = 1]
if (atomic_read(&de->count) == 0)
					if (atomic_dec_and_test(&de->count))
						if (de->deleted)
							/* also not taken! */
							free_proc_entry(de);
else
	de->deleted = 1;
		[refcount=0, deleted=1]

2) use after free

remove_proc_entry			de_put
-----------------			------
			[refcnt = 1]

					if (atomic_dec_and_test(&de->count))
if (atomic_read(&de->count) == 0)
	free_proc_entry(de);
						/* boom! */
						if (de->deleted)
							free_proc_entry(de);

BUG: unable to handle kernel paging request at virtual address 6b6b6b6b
printing eip: c10acdda *pdpt = 00000000338f8001 *pde = 0000000000000000
Oops: 0000 [#1] PREEMPT SMP
Modules linked in: af_packet ipv6 cpufreq_ondemand loop serio_raw psmouse k8temp hwmon sr_mod cdrom
Pid: 23161, comm: cat Not tainted (2.6.24-rc2-8c0863403f109a43d7000b4646da4818220d501f #4)
EIP: 0060:[] EFLAGS: 00210097 CPU: 1
EIP is at strnlen+0x6/0x18
EAX: 6b6b6b6b EBX: 6b6b6b6b ECX: 6b6b6b6b EDX: fffffffe
ESI: c128fa3b EDI: f380bf34 EBP: ffffffff ESP: f380be44
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Process cat (pid: 23161, ti=f380b000 task=f38f2570 task.ti=f380b000)
Stack: c10ac4f0 00000278 c12ce000 f43cd2a8 00000163 00000000 7da86067 00000400
       c128fa20 00896b18 f38325a8 c128fe20 ffffffff 00000000 c11f291e 00000400
       f75be300 c128fa20 f769c9a0 c10ac779 f380bf34 f7bfee70 c1018e6b f380bf34
Call Trace:
 [] vsnprintf+0x2ad/0x49b
 [] vscnprintf+0x14/0x1f
 [] vprintk+0xc5/0x2f9
 [] handle_fasteoi_irq+0x0/0xab
 [] do_IRQ+0x9f/0xb7
 [] preempt_schedule_irq+0x3f/0x5b
 [] need_resched+0x1f/0x21
 [] printk+0x1b/0x1f
 [] de_put+0x3d/0x50
 [] proc_delete_inode+0x38/0x41
 [] proc_delete_inode+0x0/0x41
 [] generic_delete_inode+0x5e/0xc6
 [] iput+0x60/0x62
 [] d_kill+0x2d/0x46
 [] dput+0xdc/0xe4
 [] __fput+0xb0/0xcd
 [] filp_close+0x48/0x4f
 [] sys_close+0x67/0xa5
 [] sysenter_past_esp+0x5f/0x85
=======================
Code: c9 74 0c f2 ae 74 05 bf 01 00 00 00 4f 89 fa 5f 89 d0 c3 85 c9 57 89 c7 89 d0 74 05 f2 ae 75 01 4f 89 f8 5f c3 89 c1 89 c8 eb 06 <80> 38 00 74 07 40 4a 83 fa ff 75 f4 29 c8 c3 90 90 90 57 83 c9
EIP: [] strnlen+0x6/0x18 SS:ESP 0068:f380be44

Also, remove broken usage of ->deleted from reiserfs: if sget() succeeds,
module is already pinned and remove_proc_entry() can't happen => nobody
can mark PDE deleted.

Dummy proc root in netns code is not marked with refcount 1. AFAICS, we
never get it, it's just for proper /proc/net removal. I double checked
CLONE_NETNS continues to work.

Patch survives many hours of modprobe/rmmod/cat loops without new bugs
which can be attributed to refcounting.

Signed-off-by: Alexey Dobriyan 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pid namespaces: make proc have multiple superblocks - one for each namespace

2007-10-19T18:53:39+00:00

Each pid namespace have to be visible through its own proc mount.  Thus we
need to have per-namespace proc trees with their own superblocks.

We cannot easily show different pid namespace via one global proc tree, since
each pid refers to different tasks in different namespaces.  E.g.  pid 1
refers to the init task in the initial namespace and to some other task when
seeing from another namespace.  Moreover - pid, exisintg in one namespace may
not exist in the other.

This approach has one move advantage is that the tasks from the init namespace
can see what tasks live in another namespace by reading entries from another
proc tree.

Signed-off-by: Pavel Emelyanov 
Cc: Oleg Nesterov 
Cc: Sukadev Bhattiprolu 
Cc: Paul Menage 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

SLAB_PANIC more (proc, posix-timers, shmem)

2007-10-17T15:42:47+00:00

These aren't modular, so SLAB_PANIC is OK.

Signed-off-by: Alexey Dobriyan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Slab API: remove useless ctor parameter and reorder parameters

2007-10-17T15:42:45+00:00

Slab constructors currently have a flags parameter that is never used.  And
the order of the arguments is opposite to other slab functions.  The object
pointer is placed before the kmem_cache pointer.

Convert

        ctor(void *object, struct kmem_cache *s, unsigned long flags)

to

        ctor(struct kmem_cache *s, void *object)

throughout the kernel

[akpm@linux-foundation.org: coupla fixes]
Signed-off-by: Christoph Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Fix select on /proc files without ->poll

2007-09-12T00:21:20+00:00

Taneli Vähäkangas  reported that commit
786d7e1612f0b0adb6046f19b906609e4fe8b1ba aka "Fix rmmod/read/write races
in /proc entries" broke SBCL + SLIME combo.

The old code in do_select() used DEFAULT_POLLMASK, if couldn't find
->poll handler.  The new code makes ->poll always there and returns 0 by
default, which is not correct.  Return DEFAULT_POLLMASK instead.

Steps to reproduce:

	install emacs, SBCL, SLIME
	emacs
	M-x slime	in *inferior-lisp* buffer
	[watch it doing "Connecting to Swank on port X.."]

Please, apply before 2.6.23.

P.S.: why SBCL can't just read(2) /proc/cpuinfo is a mystery.

Signed-off-by: Alexey Dobriyan 
Cc: T Taneli Vahakangas 
Cc: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Fix procfs compat_ioctl regression

2007-07-29T02:42:22+00:00

It is important to only provide the compat_ioctl method
if the downstream de->proc_fops does too, otherwise this
utterly confuses the logic in fs/compat_ioctl.c and we
end up doing the wrong thing.

Signed-off-by: David S. Miller 
Acked-by: Alexey Dobriyan 
Signed-off-by: Linus Torvalds

mm: Remove slab destructors from kmem_cache_create().

2007-07-20T01:11:58+00:00

Slab destructors were no longer supported after Christoph's
c59def9f222d44bb7e2f0a559f2906191a0862d7 change. They've been
BUGs for both slab and slub, and slob never supported them
either.

This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).

Signed-off-by: Paul Mundt

Fix rmmod/read/write races in /proc entries

2007-07-16T16:05:39+00:00

Fix following races:
===========================================
1. Write via ->write_proc sleeps in copy_from_user(). Module disappears
   meanwhile. Or, more generically, system call done on /proc file, method
   supplied by module is called, module dissapeares meanwhile.

   pde = create_proc_entry()
   if (!pde)
	return -ENOMEM;
   pde->write_proc = ...
				open
				write
				copy_from_user
   pde = create_proc_entry();
   if (!pde) {
	remove_proc_entry();
	return -ENOMEM;
	/* module unloaded */
   }
				*boom*
==========================================
2. bogo-revoke aka proc_kill_inodes()

  remove_proc_entry		vfs_read
  proc_kill_inodes		[check ->f_op validness]
				[check ->f_op->read validness]
				[verify_area, security permissions checks]
	->f_op = NULL;
				if (file->f_op->read)
					/* ->f_op dereference, boom */

NOTE, NOTE, NOTE: file_operations are proxied for regular files only. Let's
see how this scheme behaves, then extend if needed for directories.
Directories creators in /proc only set ->owner for them, so proxying for
directories may be unneeded.

NOTE, NOTE, NOTE: methods being proxied are ->llseek, ->read, ->write,
->poll, ->unlocked_ioctl, ->ioctl, ->compat_ioctl, ->open, ->release.
If your in-tree module uses something else, yell on me. Full audit pending.

[akpm@linux-foundation.org: build fix]
Signed-off-by: Alexey Dobriyan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Remove SLAB_CTOR_CONSTRUCTOR

2007-05-17T12:23:04+00:00

SLAB_CTOR_CONSTRUCTOR is always specified. No point in checking it.

Signed-off-by: Christoph Lameter 
Cc: David Howells 
Cc: Jens Axboe 
Cc: Steven French 
Cc: Michael Halcrow 
Cc: OGAWA Hirofumi 
Cc: Miklos Szeredi 
Cc: Steven Whitehouse 
Cc: Roman Zippel 
Cc: David Woodhouse 
Cc: Dave Kleikamp 
Cc: Trond Myklebust 
Cc: "J. Bruce Fields" 
Cc: Anton Altaparmakov 
Cc: Mark Fasheh 
Cc: Paul Mackerras 
Cc: Christoph Hellwig 
Cc: Jan Kara 
Cc: David Chinner 
Cc: "David S. Miller" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

proc: remove pathetic ->deleted WARN_ON

2007-05-08T18:15:02+00:00

WARN_ON(de && de->deleted); is sooo unreliable. Why?

proc_lookup				remove_proc_entry
===========				=================
lock_kernel();
spin_lock(&proc_subdir_lock);
[find proc entry]
spin_unlock(&proc_subdir_lock);
					spin_lock(&proc_subdir_lock);
					[find proc entry]

proc_get_inode
==============
WARN_ON(de && de->deleted);			...

					if (!atomic_read(&de->count))
						free_proc_entry(de);
					else
						de->deleted = 1;

So, if you have some strange oops [1], and doesn't see this WARN_ON it means
nothing.

[1] try_module_get() of module which doesn't exist, two lines below
    should suffice, or not?

Signed-off-by: Alexey Dobriyan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds