linux-toradex.git/drivers/android/binderfs.c, branch v5.3-rc8

binderfs: remove separate device_initcall()

2019-02-01T14:50:26+00:00

binderfs should not have a separate device_initcall(). When a kernel is
compiled with CONFIG_ANDROID_BINDERFS register the filesystem alongside
CONFIG_ANDROID_IPC. This use-case is especially sensible when users specify
CONFIG_ANDROID_IPC=y, CONFIG_ANDROID_BINDERFS=y and
ANDROID_BINDER_DEVICES="".
When CONFIG_ANDROID_BINDERFS=n then this always succeeds so there's no
regression potential for legacy workloads.

Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: respect limit on binder control creation

2019-01-30T14:23:48+00:00

We currently adhere to the reserved devices limit when creating new
binderfs devices in binderfs instances not located in the inital ipc
namespace. But it is still possible to rob the host instances of their 4
reserved devices by creating the maximum allowed number of devices in a
single binderfs instance located in a non-initial ipc namespace and then
mounting 4 separate binderfs instances in non-initial ipc namespaces. That
happens because the limit is currently not respected for the creation of
the initial binder-control device node. Block this nonsense by performing
the same check in binderfs_binder_ctl_create() that we perform in
binderfs_binder_device_create().

Fixes: 36bdf3cae09d ("binderfs: reserve devices for initial mount")
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: switch from d_add() to d_instantiate()

2019-01-22T11:25:54+00:00

In a previous commit we switched from a d_alloc_name() + d_lookup()
combination to setup a new dentry and find potential duplicates to the more
idiomatic lookup_one_len(). As far as I understand, this also means we need
to switch from d_add() to d_instantiate() since lookup_one_len() will
create a new dentry when it doesn't find an existing one and add the new
dentry to the hash queues. So we only need to call d_instantiate() to
connect the dentry to the inode and turn it into a positive dentry.

If we were to use d_add() we sure see stack traces like the following
indicating that adding the same dentry twice over the same inode:

[  744.441889] CPU: 4 PID: 2849 Comm: landscape-sysin Not tainted 5.0.0-rc1-brauner-binderfs #243
[  744.441889] Hardware name: Dell      DCS XS24-SC2          /XS24-SC2              , BIOS S59_3C20 04/07/2011
[  744.441889] RIP: 0010:__d_lookup_rcu+0x76/0x190
[  744.441889] Code: 89 75 c0 49 c1 e9 20 49 89 fd 45 89 ce 41 83 e6 07 42 8d 04 f5 00 00 00 00 89 45 c8 eb 0c 48 8b 1b 48 85 db 0f 84 81 00 00 00 <44> 8b 63 fc 4c 3b 6b 10 75 ea 48 83 7b 08 00 74 e3 41 83 e4 fe 41
[  744.441889] RSP: 0018:ffffb8c984e27ad0 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
[  744.441889] RAX: 0000000000000038 RBX: ffff9407ef770c08 RCX: ffffb8c980011000
[  744.441889] RDX: ffffb8c984e27b54 RSI: ffffb8c984e27ce0 RDI: ffff9407e6689600
[  744.441889] RBP: ffffb8c984e27b28 R08: ffffb8c984e27ba4 R09: 0000000000000007
[  744.441889] R10: ffff9407e5c4f05c R11: 973f3eb9d84a94e5 R12: 0000000000000002
[  744.441889] R13: ffff9407e6689600 R14: 0000000000000007 R15: 00000007bfef7a13
[  744.441889] FS:  00007f0db13bb740(0000) GS:ffff9407f3b00000(0000) knlGS:0000000000000000
[  744.441889] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  744.441889] CR2: 00007f0dacc51024 CR3: 000000032961a000 CR4: 00000000000006e0
[  744.441889] Call Trace:
[  744.441889]  lookup_fast+0x53/0x300
[  744.441889]  walk_component+0x49/0x350
[  744.441889]  ? inode_permission+0x63/0x1a0
[  744.441889]  link_path_walk.part.33+0x1bc/0x5a0
[  744.441889]  ? path_init+0x190/0x310
[  744.441889]  path_lookupat+0x95/0x210
[  744.441889]  filename_lookup+0xb6/0x190
[  744.441889]  ? __check_object_size+0xb8/0x1b0
[  744.441889]  ? strncpy_from_user+0x50/0x1a0
[  744.441889]  user_path_at_empty+0x36/0x40
[  744.441889]  ? user_path_at_empty+0x36/0x40
[  744.441889]  vfs_statx+0x76/0xe0
[  744.441889]  __do_sys_newstat+0x3d/0x70
[  744.441889]  __x64_sys_newstat+0x16/0x20
[  744.441889]  do_syscall_64+0x5a/0x120
[  744.441889]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  744.441889] RIP: 0033:0x7f0db0ec2775
[  744.441889] Code: 00 00 00 75 05 48 83 c4 18 c3 e8 26 55 02 00 66 0f 1f 44 00 00 83 ff 01 48 89 f0 77 30 48 89 c7 48 89 d6 b8 04 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 03 f3 c3 90 48 8b 15 e1 b6 2d 00 f7 d8 64 89
[  744.441889] RSP: 002b:00007ffc36bc9388 EFLAGS: 00000246 ORIG_RAX: 0000000000000004
[  744.441889] RAX: ffffffffffffffda RBX: 00007ffc36bc9300 RCX: 00007f0db0ec2775
[  744.441889] RDX: 00007ffc36bc9400 RSI: 00007ffc36bc9400 RDI: 00007f0dad26f050
[  744.441889] RBP: 0000000000c0bc60 R08: 0000000000000000 R09: 0000000000000001
[  744.441889] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc36bc9400
[  744.441889] R13: 0000000000000001 R14: 00000000ffffff9c R15: 0000000000c0bc60

Cc: Al Viro 
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: drop lock in binderfs_binder_ctl_create

2019-01-22T11:25:53+00:00

The binderfs_binder_ctl_create() call is a no-op on subsequent calls and
the first call is done before we unlock the suberblock. Hence, there is no
need to take inode_lock() in there. Let's remove it.

Suggested-by: Al Viro 
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: kill_litter_super() before cleanup

2019-01-22T11:25:53+00:00

Al pointed out that first calling kill_litter_super() before cleaning up
info is more correct since destroying info doesn't depend on the state of
the dentries and inodes. That the opposite remains true is not guaranteed.

Suggested-by: Al Viro 
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: rework binderfs_binder_device_create()

2019-01-22T11:25:53+00:00

- switch from d_alloc_name() + d_lookup() to lookup_one_len():
  Instead of using d_alloc_name() and then doing a d_lookup() with the
  allocated dentry to find whether a device with the name we're trying to
  create already exists switch to using lookup_one_len().  The latter will
  either return the existing dentry or a new one.

- switch from kmalloc() + strscpy() to kmemdup():
  Use a more idiomatic way to copy the name for the new dentry that
  userspace gave us.

Suggested-by: Al Viro 
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: rework binderfs_fill_super()

2019-01-22T11:25:53+00:00

Al pointed out that on binderfs_fill_super() error
deactivate_locked_super() will call binderfs_kill_super() so all of the
freeing and putting we currently do in binderfs_fill_super() is unnecessary
and buggy. Let's simply return errors and let binderfs_fill_super() take
care of cleaning up on error.

Suggested-by: Al Viro 
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: prevent renaming the control dentry

2019-01-22T11:25:53+00:00

- make binderfs control dentry immutable:
  We don't allow to unlink it since it is crucial for binderfs to be
  useable but if we allow to rename it we make the unlink trivial to
  bypass. So prevent renaming too and simply treat the control dentry as
  immutable.

- add is_binderfs_control_device() helper:
  Take the opportunity and turn the check for the control dentry into a
  separate helper is_binderfs_control_device() since it's now used in two
  places.

- simplify binderfs_rename():
  Instead of hand-rolling our custom version of simple_rename() just dumb
  the whole function down to first check whether we're trying to rename the
  control dentry. If we do EPERM the caller and if not call simple_rename().

Suggested-by: Al Viro 
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: remove outdated comment

2019-01-22T11:13:17+00:00

The comment stems from an early version of that patchset and is just
confusing now.

Cc: Al Viro 
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

binderfs: fix error return code in binderfs_fill_super()

2019-01-18T13:14:14+00:00

Fix to return a negative error code -ENOMEM from the new_inode() and
d_make_root() error handling cases instead of 0, as done elsewhere in
this function.

Fixes: 849d540ddfcd ("binderfs: implement "max" mount option")
Signed-off-by: Wei Yongjun 
Reviewed-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman