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  1. 29 7月, 2020 1 次提交
    • J
      binder: Prevent context manager from incrementing ref 0 · 4b836a14
      由 Jann Horn 提交于 
      Binder is designed such that a binder_proc never has references to
itself. If this rule is violated, memory corruption can occur when a
process sends a transaction to itself; see e.g.
<https://syzkaller.appspot.com/bug?extid=09e05aba06723a94d43d>.

There is a remaining edgecase through which such a transaction-to-self
can still occur from the context of a task with BINDER_SET_CONTEXT_MGR
access:

 - task A opens /dev/binder twice, creating binder_proc instances P1
   and P2
 - P1 becomes context manager
 - P2 calls ACQUIRE on the magic handle 0, allocating index 0 in its
   handle table
 - P1 dies (by closing the /dev/binder fd and waiting a bit)
 - P2 becomes context manager
 - P2 calls ACQUIRE on the magic handle 0, allocating index 1 in its
   handle table
   [this triggers a warning: "binder: 1974:1974 tried to acquire
   reference to desc 0, got 1 instead"]
 - task B opens /dev/binder once, creating binder_proc instance P3
 - P3 calls P2 (via magic handle 0) with (void*)1 as argument (two-way
   transaction)
 - P2 receives the handle and uses it to call P3 (two-way transaction)
 - P3 calls P2 (via magic handle 0) (two-way transaction)
 - P2 calls P2 (via handle 1) (two-way transaction)

And then, if P2 does *NOT* accept the incoming transaction work, but
instead closes the binder fd, we get a crash.

Solve it by preventing the context manager from using ACQUIRE on ref 0.
There shouldn't be any legitimate reason for the context manager to do
that.

Additionally, print a warning if someone manages to find another way to
trigger a transaction-to-self bug in the future.

Cc: stable@vger.kernel.org
Fixes: 457b9a6f ("Staging: android: add binder driver")
Acked-by: NTodd Kjos <tkjos@google.com>
Signed-off-by: NJann Horn <jannh@google.com>
Reviewed-by: NMartijn Coenen <maco@android.com>
Link: https://lore.kernel.org/r/20200727120424.1627555-1-jannh@google.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      4b836a14
  3. 23 7月, 2020 1 次提交
  5. 23 6月, 2020 1 次提交
    • T
      binder: fix null deref of proc->context · d35d3660
      由 Todd Kjos 提交于 
      The binder driver makes the assumption proc->context pointer is invariant after
initialization (as documented in the kerneldoc header for struct proc).
However, in commit f0fe2c0f ("binder: prevent UAF for binderfs devices II")
proc->context is set to NULL during binder_deferred_release().

Another proc was in the middle of setting up a transaction to the dying
process and crashed on a NULL pointer deref on "context" which is a local
set to &proc->context:

    new_ref->data.desc = (node == context->binder_context_mgr_node) ? 0 : 1;

Here's the stack:

[ 5237.855435] Call trace:
[ 5237.855441] binder_get_ref_for_node_olocked+0x100/0x2ec
[ 5237.855446] binder_inc_ref_for_node+0x140/0x280
[ 5237.855451] binder_translate_binder+0x1d0/0x388
[ 5237.855456] binder_transaction+0x2228/0x3730
[ 5237.855461] binder_thread_write+0x640/0x25bc
[ 5237.855466] binder_ioctl_write_read+0xb0/0x464
[ 5237.855471] binder_ioctl+0x30c/0x96c
[ 5237.855477] do_vfs_ioctl+0x3e0/0x700
[ 5237.855482] __arm64_sys_ioctl+0x78/0xa4
[ 5237.855488] el0_svc_common+0xb4/0x194
[ 5237.855493] el0_svc_handler+0x74/0x98
[ 5237.855497] el0_svc+0x8/0xc

The fix is to move the kfree of the binder_device to binder_free_proc()
so the binder_device is freed when we know there are no references
remaining on the binder_proc.

Fixes: f0fe2c0f ("binder: prevent UAF for binderfs devices II")
Acked-by: NChristian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: NTodd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200622200715.114382-1-tkjos@google.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      d35d3660
  7. 14 6月, 2020 1 次提交
    • M
      treewide: replace '---help---' in Kconfig files with 'help' · a7f7f624
      由 Masahiro Yamada 提交于 
      Since commit 84af7a61 ("checkpatch: kconfig: prefer 'help' over
'---help---'"), the number of '---help---' has been gradually
decreasing, but there are still more than 2400 instances.

This commit finishes the conversion. While I touched the lines,
I also fixed the indentation.

There are a variety of indentation styles found.

  a) 4 spaces + '---help---'
  b) 7 spaces + '---help---'
  c) 8 spaces + '---help---'
  d) 1 space + 1 tab + '---help---'
  e) 1 tab + '---help---'    (correct indentation)
  f) 1 tab + 1 space + '---help---'
  g) 1 tab + 2 spaces + '---help---'

In order to convert all of them to 1 tab + 'help', I ran the
following commend:

  $ find . -name 'Kconfig*' | xargs sed -i 's/^[[:space:]]*---help---/\thelp/'
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      a7f7f624
  9. 10 6月, 2020 2 次提交
  11. 23 4月, 2020 2 次提交
  13. 19 3月, 2020 1 次提交
    • C
      binderfs: port to new mount api · 095cf502
      由 Christian Brauner 提交于 
      When I first wrote binderfs the new mount api had not yet landed. Now
that it has been around for a little while and a bunch of filesystems
have already been ported we should do so too. When Al sent his
mount-api-conversion pr he requested that binderfs (and a few others) be
ported separately. It's time we port binderfs. We can make use of the
new option parser, get nicer infrastructure and it will be easier if we
ever add any new mount options.

This survives testing with the binderfs selftests:

for i in `seq 1 1000`; do ./binderfs_test; done

including the new stress tests I sent out for review today:

 TAP version 13
 1..1
 # selftests: filesystems/binderfs: binderfs_test
 # [==========] Running 3 tests from 1 test cases.
 # [ RUN      ] global.binderfs_stress
 # [  XFAIL!  ] Tests are not run as root. Skipping privileged tests
 # [==========] Running 3 tests from 1 test cases.
 # [ RUN      ] global.binderfs_stress
 # [       OK ] global.binderfs_stress
 # [ RUN      ] global.binderfs_test_privileged
 # [       OK ] global.binderfs_test_privileged
 # [ RUN      ] global.binderfs_test_unprivileged
 # # Allocated new binder device with major 243, minor 4, and name my-binder
 # # Detected binder version: 8
 # [==========] Running 3 tests from 1 test cases.
 # [ RUN      ] global.binderfs_stress
 # [       OK ] global.binderfs_stress
 # [ RUN      ] global.binderfs_test_privileged
 # [       OK ] global.binderfs_test_privileged
 # [ RUN      ] global.binderfs_test_unprivileged
 # [       OK ] global.binderfs_test_unprivileged
 # [==========] 3 / 3 tests passed.
 # [  PASSED  ]
 ok 1 selftests: filesystems/binderfs: binderfs_test

Cc: Todd Kjos <tkjos@google.com>
Signed-off-by: NChristian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200313153427.141789-1-christian.brauner@ubuntu.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      095cf502
  15. 12 3月, 2020 1 次提交
  17. 04 3月, 2020 1 次提交
    • C
      binder: prevent UAF for binderfs devices II · f0fe2c0f
      由 Christian Brauner 提交于 
      This is a necessary follow up to the first fix I proposed and we merged
in 2669b8b0 ("binder: prevent UAF for binderfs devices"). I have been
overly optimistic that the simple fix I proposed would work. But alas,
ihold() + iput() won't work since the inodes won't survive the
destruction of the superblock.
So all we get with my prior fix is a different race with a tinier
race-window but it doesn't solve the issue. Fwiw, the problem lies with
generic_shutdown_super(). It even has this cozy Al-style comment:

          if (!list_empty(&sb->s_inodes)) {
                  printk("VFS: Busy inodes after unmount of %s. "
                     "Self-destruct in 5 seconds.  Have a nice day...\n",
                     sb->s_id);
          }

On binder_release(), binder_defer_work(proc, BINDER_DEFERRED_RELEASE) is
called which punts the actual cleanup operation to a workqueue. At some
point, binder_deferred_func() will be called which will end up calling
binder_deferred_release() which will retrieve and cleanup the
binder_context attach to this struct binder_proc.

If we trace back where this binder_context is attached to binder_proc we
see that it is set in binder_open() and is taken from the struct
binder_device it is associated with. This obviously assumes that the
struct binder_device that context is attached to is _never_ freed. While
that might be true for devtmpfs binder devices it is most certainly
wrong for binderfs binder devices.

So, assume binder_open() is called on a binderfs binder devices. We now
stash away the struct binder_context associated with that struct
binder_devices:
	proc->context = &binder_dev->context;
	/* binderfs stashes devices in i_private */
	if (is_binderfs_device(nodp)) {
		binder_dev = nodp->i_private;
		info = nodp->i_sb->s_fs_info;
		binder_binderfs_dir_entry_proc = info->proc_log_dir;
	} else {
	.
	.
	.
	proc->context = &binder_dev->context;

Now let's assume that the binderfs instance for that binder devices is
shutdown via umount() and/or the mount namespace associated with it goes
away. As long as there is still an fd open for that binderfs binder
device things are fine. But let's assume we now close the last fd for
that binderfs binder device. Now binder_release() is called and punts to
the workqueue. Assume that the workqueue has quite a bit of stuff to do
and doesn't get to cleaning up the struct binder_proc and the associated
struct binder_context with it for that binderfs binder device right
away. In the meantime, the VFS is killing the super block and is
ultimately calling sb->evict_inode() which means it will call
binderfs_evict_inode() which does:

static void binderfs_evict_inode(struct inode *inode)
{
	struct binder_device *device = inode->i_private;
	struct binderfs_info *info = BINDERFS_I(inode);

	clear_inode(inode);

	if (!S_ISCHR(inode->i_mode) || !device)
		return;

	mutex_lock(&binderfs_minors_mutex);
	--info->device_count;
	ida_free(&binderfs_minors, device->miscdev.minor);
	mutex_unlock(&binderfs_minors_mutex);

	kfree(device->context.name);
	kfree(device);
}

thereby freeing the struct binder_device including struct
binder_context.

Now the workqueue finally has time to get around to cleaning up struct
binder_proc and is now trying to access the associate struct
binder_context. Since it's already freed it will OOPs.

Fix this by introducing a refounct on binder devices.

This is an alternative fix to 51d8a7ec ("binder: prevent UAF read in
print_binder_transaction_log_entry()").

Fixes: 3ad20fe3 ("binder: implement binderfs")
Fixes: 2669b8b0 ("binder: prevent UAF for binderfs devices")
Fixes: 03e2e07e ("binder: Make transaction_log available in binderfs")
Related : 51d8a7ec ("binder: prevent UAF read in print_binder_transaction_log_entry()")
Cc: stable@vger.kernel.org
Signed-off-by: NChristian Brauner <christian.brauner@ubuntu.com>
Acked-by: NTodd Kjos <tkjos@google.com>
Link: https://lore.kernel.org/r/20200303164340.670054-1-christian.brauner@ubuntu.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      f0fe2c0f
  19. 03 3月, 2020 1 次提交
    • C
      binder: prevent UAF for binderfs devices · 2669b8b0
      由 Christian Brauner 提交于 
      On binder_release(), binder_defer_work(proc, BINDER_DEFERRED_RELEASE) is
called which punts the actual cleanup operation to a workqueue. At some
point, binder_deferred_func() will be called which will end up calling
binder_deferred_release() which will retrieve and cleanup the
binder_context attach to this struct binder_proc.

If we trace back where this binder_context is attached to binder_proc we
see that it is set in binder_open() and is taken from the struct
binder_device it is associated with. This obviously assumes that the
struct binder_device that context is attached to is _never_ freed. While
that might be true for devtmpfs binder devices it is most certainly
wrong for binderfs binder devices.

So, assume binder_open() is called on a binderfs binder devices. We now
stash away the struct binder_context associated with that struct
binder_devices:
	proc->context = &binder_dev->context;
	/* binderfs stashes devices in i_private */
	if (is_binderfs_device(nodp)) {
		binder_dev = nodp->i_private;
		info = nodp->i_sb->s_fs_info;
		binder_binderfs_dir_entry_proc = info->proc_log_dir;
	} else {
	.
	.
	.
	proc->context = &binder_dev->context;

Now let's assume that the binderfs instance for that binder devices is
shutdown via umount() and/or the mount namespace associated with it goes
away. As long as there is still an fd open for that binderfs binder
device things are fine. But let's assume we now close the last fd for
that binderfs binder device. Now binder_release() is called and punts to
the workqueue. Assume that the workqueue has quite a bit of stuff to do
and doesn't get to cleaning up the struct binder_proc and the associated
struct binder_context with it for that binderfs binder device right
away. In the meantime, the VFS is killing the super block and is
ultimately calling sb->evict_inode() which means it will call
binderfs_evict_inode() which does:

static void binderfs_evict_inode(struct inode *inode)
{
	struct binder_device *device = inode->i_private;
	struct binderfs_info *info = BINDERFS_I(inode);

	clear_inode(inode);

	if (!S_ISCHR(inode->i_mode) || !device)
		return;

	mutex_lock(&binderfs_minors_mutex);
	--info->device_count;
	ida_free(&binderfs_minors, device->miscdev.minor);
	mutex_unlock(&binderfs_minors_mutex);

	kfree(device->context.name);
	kfree(device);
}

thereby freeing the struct binder_device including struct
binder_context.

Now the workqueue finally has time to get around to cleaning up struct
binder_proc and is now trying to access the associate struct
binder_context. Since it's already freed it will OOPs.

Fix this by holding an additional reference to the inode that is only
released once the workqueue is done cleaning up struct binder_proc. This
is an easy alternative to introducing separate refcounting on struct
binder_device which we can always do later if it becomes necessary.

This is an alternative fix to 51d8a7ec ("binder: prevent UAF read in
print_binder_transaction_log_entry()").

Fixes: 3ad20fe3 ("binder: implement binderfs")
Fixes: 03e2e07e ("binder: Make transaction_log available in binderfs")
Related : 51d8a7ec ("binder: prevent UAF read in print_binder_transaction_log_entry()")
Cc: stable@vger.kernel.org
Signed-off-by: NChristian Brauner <christian.brauner@ubuntu.com>
Acked-by: NTodd Kjos <tkjos@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      2669b8b0
  21. 22 1月, 2020 1 次提交
  23. 21 1月, 2020 1 次提交
  25. 14 12月, 2019 1 次提交
  27. 14 11月, 2019 3 次提交
  29. 23 10月, 2019 1 次提交
  31. 22 10月, 2019 1 次提交
  33. 17 10月, 2019 2 次提交
  35. 10 10月, 2019 2 次提交
  37. 04 9月, 2019 6 次提交
  39. 24 7月, 2019 2 次提交
  41. 01 7月, 2019 1 次提交
  43. 22 6月, 2019 1 次提交
  45. 13 6月, 2019 1 次提交
  47. 05 6月, 2019 1 次提交
  49. 21 5月, 2019 1 次提交
  51. 26 4月, 2019 1 次提交
  53. 25 4月, 2019 1 次提交
  55. 21 3月, 2019 1 次提交