linux-stable.git/drivers/android/binder.c, branch linux-5.10.y Linux kernel stable tree binder: don't use %pK through printk 2026-03-04T12:20:06+00:00 Thomas Weißschuh thomas.weissschuh@linutronix.de 2026-01-07T14:29:50+00:00 0e5513d799fec53ede90236290fefe9ef2b692a2 [ Upstream commit 56d21267663bad91e8b10121224ec46366a7937e ] In the past %pK was preferable to %p as it would not leak raw pointer values into the kernel log. Since commit ad67b74d2469 ("printk: hash addresses printed with %p") the regular %p has been improved to avoid this issue. Furthermore, restricted pointers ("%pK") were never meant to be used through printk(). They can still unintentionally leak raw pointers or acquire sleeping locks in atomic contexts. Switch to the regular pointer formatting which is safer and easier to reason about. There are still a few users of %pK left, but these use it through seq_file, for which its usage is safe. Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> Acked-by: Carlos Llamas <cmllamas@google.com> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Link: https://patch.msgid.link/20260107-restricted-pointers-binder-v1-1-181018bf3812@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 56d21267663bad91e8b10121224ec46366a7937e ]

In the past %pK was preferable to %p as it would not leak raw pointer
values into the kernel log. Since commit ad67b74d2469 ("printk: hash
addresses printed with %p") the regular %p has been improved to avoid
this issue. Furthermore, restricted pointers ("%pK") were never meant
to be used through printk(). They can still unintentionally leak raw
pointers or acquire sleeping locks in atomic contexts.

Switch to the regular pointer formatting which is safer and
easier to reason about.

There are still a few users of %pK left, but these use it through
seq_file, for which its usage is safe.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Carlos Llamas <cmllamas@google.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260107-restricted-pointers-binder-v1-1-181018bf3812@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
binder: remove "invalid inc weak" check 2025-10-29T13:01:22+00:00 Alice Ryhl aliceryhl@google.com 2025-10-15T14:26:55+00:00 1677f31bfe1578fb18c83fc37125c6fb701fb9c2 commit d90eeb8ecd227c204ab6c34a17b372bd950b7aa2 upstream. There are no scenarios where a weak increment is invalid on binder_node. The only possible case where it could be invalid is if the kernel delivers BR_DECREFS to the process that owns the node, and then increments the weak refcount again, effectively "reviving" a dead node. However, that is not possible: when the BR_DECREFS command is delivered, the kernel removes and frees the binder_node. The fact that you were able to call binder_inc_node_nilocked() implies that the node is not yet destroyed, which implies that BR_DECREFS has not been delivered to userspace, so incrementing the weak refcount is valid. Note that it's currently possible to trigger this condition if the owner calls BINDER_THREAD_EXIT while node->has_weak_ref is true. This causes BC_INCREFS on binder_ref instances to fail when they should not. Cc: stable@vger.kernel.org Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") Reported-by: Yu-Ting Tseng <yutingtseng@google.com> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://patch.msgid.link/20251015-binder-weak-inc-v1-1-7914b092c371@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit d90eeb8ecd227c204ab6c34a17b372bd950b7aa2 upstream.

There are no scenarios where a weak increment is invalid on binder_node.
The only possible case where it could be invalid is if the kernel
delivers BR_DECREFS to the process that owns the node, and then
increments the weak refcount again, effectively "reviving" a dead node.

However, that is not possible: when the BR_DECREFS command is delivered,
the kernel removes and frees the binder_node. The fact that you were
able to call binder_inc_node_nilocked() implies that the node is not yet
destroyed, which implies that BR_DECREFS has not been delivered to
userspace, so incrementing the weak refcount is valid.

Note that it's currently possible to trigger this condition if the owner
calls BINDER_THREAD_EXIT while node->has_weak_ref is true. This causes
BC_INCREFS on binder_ref instances to fail when they should not.

Cc: stable@vger.kernel.org
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Reported-by: Yu-Ting Tseng <yutingtseng@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20251015-binder-weak-inc-v1-1-7914b092c371@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
binder: fix UAF caused by offsets overwrite 2024-09-12T09:06:50+00:00 Carlos Llamas cmllamas@google.com 2024-08-22T18:23:52+00:00 3a8154bb4ab4a01390a3abf1e6afac296e037da4 commit 4df153652cc46545722879415937582028c18af5 upstream. Binder objects are processed and copied individually into the target buffer during transactions. Any raw data in-between these objects is copied as well. However, this raw data copy lacks an out-of-bounds check. If the raw data exceeds the data section size then the copy overwrites the offsets section. This eventually triggers an error that attempts to unwind the processed objects. However, at this point the offsets used to index these objects are now corrupted. Unwinding with corrupted offsets can result in decrements of arbitrary nodes and lead to their premature release. Other users of such nodes are left with a dangling pointer triggering a use-after-free. This issue is made evident by the following KASAN report (trimmed): ================================================================== BUG: KASAN: slab-use-after-free in _raw_spin_lock+0xe4/0x19c Write of size 4 at addr ffff47fc91598f04 by task binder-util/743 CPU: 9 UID: 0 PID: 743 Comm: binder-util Not tainted 6.11.0-rc4 #1 Hardware name: linux,dummy-virt (DT) Call trace: _raw_spin_lock+0xe4/0x19c binder_free_buf+0x128/0x434 binder_thread_write+0x8a4/0x3260 binder_ioctl+0x18f0/0x258c [...] Allocated by task 743: __kmalloc_cache_noprof+0x110/0x270 binder_new_node+0x50/0x700 binder_transaction+0x413c/0x6da8 binder_thread_write+0x978/0x3260 binder_ioctl+0x18f0/0x258c [...] Freed by task 745: kfree+0xbc/0x208 binder_thread_read+0x1c5c/0x37d4 binder_ioctl+0x16d8/0x258c [...] ================================================================== To avoid this issue, let's check that the raw data copy is within the boundaries of the data section. Fixes: 6d98eb95b450 ("binder: avoid potential data leakage when copying txn") Cc: Todd Kjos <tkjos@google.com> Cc: stable@vger.kernel.org Signed-off-by: Carlos Llamas <cmllamas@google.com> Link: https://lore.kernel.org/r/20240822182353.2129600-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 4df153652cc46545722879415937582028c18af5 upstream.

Binder objects are processed and copied individually into the target
buffer during transactions. Any raw data in-between these objects is
copied as well. However, this raw data copy lacks an out-of-bounds
check. If the raw data exceeds the data section size then the copy
overwrites the offsets section. This eventually triggers an error that
attempts to unwind the processed objects. However, at this point the
offsets used to index these objects are now corrupted.

Unwinding with corrupted offsets can result in decrements of arbitrary
nodes and lead to their premature release. Other users of such nodes are
left with a dangling pointer triggering a use-after-free. This issue is
made evident by the following KASAN report (trimmed):

  ==================================================================
  BUG: KASAN: slab-use-after-free in _raw_spin_lock+0xe4/0x19c
  Write of size 4 at addr ffff47fc91598f04 by task binder-util/743

  CPU: 9 UID: 0 PID: 743 Comm: binder-util Not tainted 6.11.0-rc4 #1
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   _raw_spin_lock+0xe4/0x19c
   binder_free_buf+0x128/0x434
   binder_thread_write+0x8a4/0x3260
   binder_ioctl+0x18f0/0x258c
  [...]

  Allocated by task 743:
   __kmalloc_cache_noprof+0x110/0x270
   binder_new_node+0x50/0x700
   binder_transaction+0x413c/0x6da8
   binder_thread_write+0x978/0x3260
   binder_ioctl+0x18f0/0x258c
  [...]

  Freed by task 745:
   kfree+0xbc/0x208
   binder_thread_read+0x1c5c/0x37d4
   binder_ioctl+0x16d8/0x258c
  [...]
  ==================================================================

To avoid this issue, let's check that the raw data copy is within the
boundaries of the data section.

Fixes: 6d98eb95b450 ("binder: avoid potential data leakage when copying txn")
Cc: Todd Kjos <tkjos@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20240822182353.2129600-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
binder: fix hang of unregistered readers 2024-08-19T03:40:58+00:00 Carlos Llamas cmllamas@google.com 2024-07-11T20:14:51+00:00 388ee7a4d33045933553542aec4530d859db7c29 commit 31643d84b8c3d9c846aa0e20bc033e46c68c7e7d upstream. With the introduction of binder_available_for_proc_work_ilocked() in commit 1b77e9dcc3da ("ANDROID: binder: remove proc waitqueue") a binder thread can only "wait_for_proc_work" after its thread->looper has been marked as BINDER_LOOPER_STATE_{ENTERED|REGISTERED}. This means an unregistered reader risks waiting indefinitely for work since it never gets added to the proc->waiting_threads. If there are no further references to its waitqueue either the task will hang. The same applies to readers using the (e)poll interface. I couldn't find the rationale behind this restriction. So this patch restores the previous behavior of allowing unregistered threads to "wait_for_proc_work". Note that an error message for this scenario, which had previously become unreachable, is now re-enabled. Fixes: 1b77e9dcc3da ("ANDROID: binder: remove proc waitqueue") Cc: stable@vger.kernel.org Cc: Martijn Coenen <maco@google.com> Cc: Arve Hjønnevåg <arve@google.com> Signed-off-by: Carlos Llamas <cmllamas@google.com> Link: https://lore.kernel.org/r/20240711201452.2017543-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 31643d84b8c3d9c846aa0e20bc033e46c68c7e7d upstream.

With the introduction of binder_available_for_proc_work_ilocked() in
commit 1b77e9dcc3da ("ANDROID: binder: remove proc waitqueue") a binder
thread can only "wait_for_proc_work" after its thread->looper has been
marked as BINDER_LOOPER_STATE_{ENTERED|REGISTERED}.

This means an unregistered reader risks waiting indefinitely for work
since it never gets added to the proc->waiting_threads. If there are no
further references to its waitqueue either the task will hang. The same
applies to readers using the (e)poll interface.

I couldn't find the rationale behind this restriction. So this patch
restores the previous behavior of allowing unregistered threads to
"wait_for_proc_work". Note that an error message for this scenario,
which had previously become unreachable, is now re-enabled.

Fixes: 1b77e9dcc3da ("ANDROID: binder: remove proc waitqueue")
Cc: stable@vger.kernel.org
Cc: Martijn Coenen <maco@google.com>
Cc: Arve Hjønnevåg <arve@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20240711201452.2017543-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
binder: fix max_thread type inconsistency 2024-06-16T11:32:30+00:00 Carlos Llamas cmllamas@google.com 2024-04-21T17:37:49+00:00 75805481c35d05d6d56db175d8f020c2948a3e3a commit 42316941335644a98335f209daafa4c122f28983 upstream. The type defined for the BINDER_SET_MAX_THREADS ioctl was changed from size_t to __u32 in order to avoid incompatibility issues between 32 and 64-bit kernels. However, the internal types used to copy from user and store the value were never updated. Use u32 to fix the inconsistency. Fixes: a9350fc859ae ("staging: android: binder: fix BINDER_SET_MAX_THREADS declaration") Reported-by: Arve Hjønnevåg <arve@android.com> Cc: stable@vger.kernel.org Signed-off-by: Carlos Llamas <cmllamas@google.com> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240421173750.3117808-1-cmllamas@google.com [cmllamas: resolve minor conflicts due to missing commit 421518a2740f] Signed-off-by: Carlos Llamas <cmllamas@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 42316941335644a98335f209daafa4c122f28983 upstream.

The type defined for the BINDER_SET_MAX_THREADS ioctl was changed from
size_t to __u32 in order to avoid incompatibility issues between 32 and
64-bit kernels. However, the internal types used to copy from user and
store the value were never updated. Use u32 to fix the inconsistency.

Fixes: a9350fc859ae ("staging: android: binder: fix BINDER_SET_MAX_THREADS declaration")
Reported-by: Arve Hjønnevåg <arve@android.com>
Cc: stable@vger.kernel.org
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240421173750.3117808-1-cmllamas@google.com
[cmllamas: resolve minor conflicts due to missing commit 421518a2740f]
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
binder: check offset alignment in binder_get_object() 2024-05-02T14:23:38+00:00 Carlos Llamas cmllamas@google.com 2024-03-30T19:01:14+00:00 48a1f83ca9c68518b1a783c62e6a8223144fa9fc commit aaef73821a3b0194a01bd23ca77774f704a04d40 upstream. Commit 6d98eb95b450 ("binder: avoid potential data leakage when copying txn") introduced changes to how binder objects are copied. In doing so, it unintentionally removed an offset alignment check done through calls to binder_alloc_copy_from_buffer() -> check_buffer(). These calls were replaced in binder_get_object() with copy_from_user(), so now an explicit offset alignment check is needed here. This avoids later complications when unwinding the objects gets harder. It is worth noting this check existed prior to commit 7a67a39320df ("binder: add function to copy binder object from buffer"), likely removed due to redundancy at the time. Fixes: 6d98eb95b450 ("binder: avoid potential data leakage when copying txn") Cc: stable@vger.kernel.org Signed-off-by: Carlos Llamas <cmllamas@google.com> Acked-by: Todd Kjos <tkjos@google.com> Link: https://lore.kernel.org/r/20240330190115.1877819-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit aaef73821a3b0194a01bd23ca77774f704a04d40 upstream.

Commit 6d98eb95b450 ("binder: avoid potential data leakage when copying
txn") introduced changes to how binder objects are copied. In doing so,
it unintentionally removed an offset alignment check done through calls
to binder_alloc_copy_from_buffer() -> check_buffer().

These calls were replaced in binder_get_object() with copy_from_user(),
so now an explicit offset alignment check is needed here. This avoids
later complications when unwinding the objects gets harder.

It is worth noting this check existed prior to commit 7a67a39320df
("binder: add function to copy binder object from buffer"), likely
removed due to redundancy at the time.

Fixes: 6d98eb95b450 ("binder: avoid potential data leakage when copying txn")
Cc: stable@vger.kernel.org
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Acked-by: Todd Kjos <tkjos@google.com>
Link: https://lore.kernel.org/r/20240330190115.1877819-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
binder: signal epoll threads of self-work 2024-02-23T07:42:26+00:00 Carlos Llamas cmllamas@google.com 2024-01-31T21:53:46+00:00 a423042052ec2bdbf1e552e621e6a768922363cc commit 97830f3c3088638ff90b20dfba2eb4d487bf14d7 upstream. In (e)poll mode, threads often depend on I/O events to determine when data is ready for consumption. Within binder, a thread may initiate a command via BINDER_WRITE_READ without a read buffer and then make use of epoll_wait() or similar to consume any responses afterwards. It is then crucial that epoll threads are signaled via wakeup when they queue their own work. Otherwise, they risk waiting indefinitely for an event leaving their work unhandled. What is worse, subsequent commands won't trigger a wakeup either as the thread has pending work. Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") Cc: Arve Hjønnevåg <arve@android.com> Cc: Martijn Coenen <maco@android.com> Cc: Alice Ryhl <aliceryhl@google.com> Cc: Steven Moreland <smoreland@google.com> Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Carlos Llamas <cmllamas@google.com> Link: https://lore.kernel.org/r/20240131215347.1808751-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 97830f3c3088638ff90b20dfba2eb4d487bf14d7 upstream.

In (e)poll mode, threads often depend on I/O events to determine when
data is ready for consumption. Within binder, a thread may initiate a
command via BINDER_WRITE_READ without a read buffer and then make use
of epoll_wait() or similar to consume any responses afterwards.

It is then crucial that epoll threads are signaled via wakeup when they
queue their own work. Otherwise, they risk waiting indefinitely for an
event leaving their work unhandled. What is worse, subsequent commands
won't trigger a wakeup either as the thread has pending work.

Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Martijn Coenen <maco@android.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Steven Moreland <smoreland@google.com>
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20240131215347.1808751-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
binder: use EPOLLERR from eventpoll.h 2024-01-25T22:37:38+00:00 Carlos Llamas cmllamas@google.com 2023-12-01T17:21:30+00:00 e18d60757bcac58384169ad5c33d48b9c95a31dd commit 6ac061db9c58ca5b9270b1b3940d2464fb3ff183 upstream. Use EPOLLERR instead of POLLERR to make sure it is cast to the correct __poll_t type. This fixes the following sparse issue: drivers/android/binder.c:5030:24: warning: incorrect type in return expression (different base types) drivers/android/binder.c:5030:24: expected restricted __poll_t drivers/android/binder.c:5030:24: got int Fixes: f88982679f54 ("binder: check for binder_thread allocation failure in binder_poll()") Cc: stable@vger.kernel.org Cc: Eric Biggers <ebiggers@google.com> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Signed-off-by: Carlos Llamas <cmllamas@google.com> Link: https://lore.kernel.org/r/20231201172212.1813387-2-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 6ac061db9c58ca5b9270b1b3940d2464fb3ff183 upstream.

Use EPOLLERR instead of POLLERR to make sure it is cast to the correct
__poll_t type. This fixes the following sparse issue:

  drivers/android/binder.c:5030:24: warning: incorrect type in return expression (different base types)
  drivers/android/binder.c:5030:24:    expected restricted __poll_t
  drivers/android/binder.c:5030:24:    got int

Fixes: f88982679f54 ("binder: check for binder_thread allocation failure in binder_poll()")
Cc: stable@vger.kernel.org
Cc: Eric Biggers <ebiggers@google.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20231201172212.1813387-2-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
binder: fix memory leak in binder_init() 2023-08-16T16:21:00+00:00 Qi Zheng zhengqi.arch@bytedance.com 2023-06-25T15:49:37+00:00 d7e5e2b87f5d27469075b6326b6b358e38cd9dcb commit adb9743d6a08778b78d62d16b4230346d3508986 upstream. In binder_init(), the destruction of binder_alloc_shrinker_init() is not performed in the wrong path, which will cause memory leaks. So this commit introduces binder_alloc_shrinker_exit() and calls it in the wrong path to fix that. Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> Acked-by: Carlos Llamas <cmllamas@google.com> Fixes: f2517eb76f1f ("android: binder: Add global lru shrinker to binder") Cc: stable <stable@kernel.org> Link: https://lore.kernel.org/r/20230625154937.64316-1-qi.zheng@linux.dev Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit adb9743d6a08778b78d62d16b4230346d3508986 upstream.

In binder_init(), the destruction of binder_alloc_shrinker_init() is not
performed in the wrong path, which will cause memory leaks. So this commit
introduces binder_alloc_shrinker_exit() and calls it in the wrong path to
fix that.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Carlos Llamas <cmllamas@google.com>
Fixes: f2517eb76f1f ("android: binder: Add global lru shrinker to binder")
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/r/20230625154937.64316-1-qi.zheng@linux.dev
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
binder: fix UAF caused by faulty buffer cleanup 2023-06-05T07:07:04+00:00 Carlos Llamas cmllamas@google.com 2023-05-05T20:30:20+00:00 2218752325a98861dfb10f59a9b0270d6d4abe21 commit bdc1c5fac982845a58d28690cdb56db8c88a530d upstream. In binder_transaction_buffer_release() the 'failed_at' offset indicates the number of objects to clean up. However, this function was changed by commit 44d8047f1d87 ("binder: use standard functions to allocate fds"), to release all the objects in the buffer when 'failed_at' is zero. This introduced an issue when a transaction buffer is released without any objects having been processed so far. In this case, 'failed_at' is indeed zero yet it is misinterpreted as releasing the entire buffer. This leads to use-after-free errors where nodes are incorrectly freed and subsequently accessed. Such is the case in the following KASAN report: ================================================================== BUG: KASAN: slab-use-after-free in binder_thread_read+0xc40/0x1f30 Read of size 8 at addr ffff4faf037cfc58 by task poc/474 CPU: 6 PID: 474 Comm: poc Not tainted 6.3.0-12570-g7df047b3f0aa #5 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x94/0xec show_stack+0x18/0x24 dump_stack_lvl+0x48/0x60 print_report+0xf8/0x5b8 kasan_report+0xb8/0xfc __asan_load8+0x9c/0xb8 binder_thread_read+0xc40/0x1f30 binder_ioctl+0xd9c/0x1768 __arm64_sys_ioctl+0xd4/0x118 invoke_syscall+0x60/0x188 [...] Allocated by task 474: kasan_save_stack+0x3c/0x64 kasan_set_track+0x2c/0x40 kasan_save_alloc_info+0x24/0x34 __kasan_kmalloc+0xb8/0xbc kmalloc_trace+0x48/0x5c binder_new_node+0x3c/0x3a4 binder_transaction+0x2b58/0x36f0 binder_thread_write+0x8e0/0x1b78 binder_ioctl+0x14a0/0x1768 __arm64_sys_ioctl+0xd4/0x118 invoke_syscall+0x60/0x188 [...] Freed by task 475: kasan_save_stack+0x3c/0x64 kasan_set_track+0x2c/0x40 kasan_save_free_info+0x38/0x5c __kasan_slab_free+0xe8/0x154 __kmem_cache_free+0x128/0x2bc kfree+0x58/0x70 binder_dec_node_tmpref+0x178/0x1fc binder_transaction_buffer_release+0x430/0x628 binder_transaction+0x1954/0x36f0 binder_thread_write+0x8e0/0x1b78 binder_ioctl+0x14a0/0x1768 __arm64_sys_ioctl+0xd4/0x118 invoke_syscall+0x60/0x188 [...] ================================================================== In order to avoid these issues, let's always calculate the intended 'failed_at' offset beforehand. This is renamed and wrapped in a helper function to make it clear and convenient. Fixes: 32e9f56a96d8 ("binder: don't detect sender/target during buffer cleanup") Reported-by: Zi Fan Tan <zifantan@google.com> Cc: stable@vger.kernel.org Signed-off-by: Carlos Llamas <cmllamas@google.com> Acked-by: Todd Kjos <tkjos@google.com> Link: https://lore.kernel.org/r/20230505203020.4101154-1-cmllamas@google.com [cmllamas: resolve trivial conflict due to missing commit 9864bb4801331] Signed-off-by: Carlos Llamas <cmllamas@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit bdc1c5fac982845a58d28690cdb56db8c88a530d upstream.

In binder_transaction_buffer_release() the 'failed_at' offset indicates
the number of objects to clean up. However, this function was changed by
commit 44d8047f1d87 ("binder: use standard functions to allocate fds"),
to release all the objects in the buffer when 'failed_at' is zero.

This introduced an issue when a transaction buffer is released without
any objects having been processed so far. In this case, 'failed_at' is
indeed zero yet it is misinterpreted as releasing the entire buffer.

This leads to use-after-free errors where nodes are incorrectly freed
and subsequently accessed. Such is the case in the following KASAN
report:

  ==================================================================
  BUG: KASAN: slab-use-after-free in binder_thread_read+0xc40/0x1f30
  Read of size 8 at addr ffff4faf037cfc58 by task poc/474

  CPU: 6 PID: 474 Comm: poc Not tainted 6.3.0-12570-g7df047b3f0aa #5
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   dump_backtrace+0x94/0xec
   show_stack+0x18/0x24
   dump_stack_lvl+0x48/0x60
   print_report+0xf8/0x5b8
   kasan_report+0xb8/0xfc
   __asan_load8+0x9c/0xb8
   binder_thread_read+0xc40/0x1f30
   binder_ioctl+0xd9c/0x1768
   __arm64_sys_ioctl+0xd4/0x118
   invoke_syscall+0x60/0x188
  [...]

  Allocated by task 474:
   kasan_save_stack+0x3c/0x64
   kasan_set_track+0x2c/0x40
   kasan_save_alloc_info+0x24/0x34
   __kasan_kmalloc+0xb8/0xbc
   kmalloc_trace+0x48/0x5c
   binder_new_node+0x3c/0x3a4
   binder_transaction+0x2b58/0x36f0
   binder_thread_write+0x8e0/0x1b78
   binder_ioctl+0x14a0/0x1768
   __arm64_sys_ioctl+0xd4/0x118
   invoke_syscall+0x60/0x188
  [...]

  Freed by task 475:
   kasan_save_stack+0x3c/0x64
   kasan_set_track+0x2c/0x40
   kasan_save_free_info+0x38/0x5c
   __kasan_slab_free+0xe8/0x154
   __kmem_cache_free+0x128/0x2bc
   kfree+0x58/0x70
   binder_dec_node_tmpref+0x178/0x1fc
   binder_transaction_buffer_release+0x430/0x628
   binder_transaction+0x1954/0x36f0
   binder_thread_write+0x8e0/0x1b78
   binder_ioctl+0x14a0/0x1768
   __arm64_sys_ioctl+0xd4/0x118
   invoke_syscall+0x60/0x188
  [...]
  ==================================================================

In order to avoid these issues, let's always calculate the intended
'failed_at' offset beforehand. This is renamed and wrapped in a helper
function to make it clear and convenient.

Fixes: 32e9f56a96d8 ("binder: don't detect sender/target during buffer cleanup")
Reported-by: Zi Fan Tan <zifantan@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Acked-by: Todd Kjos <tkjos@google.com>
Link: https://lore.kernel.org/r/20230505203020.4101154-1-cmllamas@google.com
[cmllamas: resolve trivial conflict due to missing commit 9864bb4801331]
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>