kernel/git/stable/linux-stable.git/drivers/android/binder.c, branch linux-6.18.y

binder: fix UAF in binder_free_transaction()

2026-07-18T14:53:11+00:00

commit f223d27a546c1e1f48d38fd67760e78f068fe8c4 upstream. In binder_free_transaction(), the t->to_proc is read under the t->lock. However, once the t->lock is dropped, the to_proc can die in parallel. This leads to a use-after-free error when we attempt to acquire its inner lock right afterwards: ================================================================== BUG: KASAN: slab-use-after-free in _raw_spin_lock+0xe4/0x1a0 Write of size 4 at addr ffff00001125da70 by task B/672 CPU: 20 UID: 0 PID: 672 Comm: B Not tainted 7.1.0-rc6-00284-g8e65320d91cd #4 PREEMPT Hardware name: linux,dummy-virt (DT) Call trace: _raw_spin_lock+0xe4/0x1a0 binder_free_transaction+0x8c/0x320 binder_send_failed_reply+0x21c/0x2f8 binder_thread_release+0x488/0x7e0 binder_ioctl+0x12c0/0x29a0 [...] Allocated by task 675: __kmalloc_cache_noprof+0x174/0x444 binder_open+0x118/0xb70 do_dentry_open+0x374/0x1040 vfs_open+0x58/0x3bc [...] Freed by task 212: __kasan_slab_free+0x58/0x80 kfree+0x1a0/0x4a4 binder_proc_dec_tmpref+0x32c/0x5e0 binder_deferred_func+0xc48/0x104c process_one_work+0x53c/0xbc0 [...] ================================================================== To prevent this, pin the target thread (t->to_thread) to guarantee the target process remains alive. Undelivered transactions without a target thread are already safe, as the target process can only be the current context in those paths. Cc: stable Reported-by: Alice Ryhl Closes: https://lore.kernel.org/all/aikJKVuny_eOivwN@google.com/ Fixes: a370003cc301 ("binder: fix possible UAF when freeing buffer") Signed-off-by: Carlos Llamas Reviewed-by: Alice Ryhl Link: https://patch.msgid.link/20260619185233.2194678-2-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman

binder: fix UAF in binder_thread_release()

2026-07-18T14:53:11+00:00

commit 114a116aaa5f0295376cdf12da743c5bce3b20ce upstream. When a thread exits, binder_thread_release() walks its transaction stack to clear the t->from and t->to_proc that correspond with the exiting thread. However, a process dying in parallel might attempt to kfree some of these transactions. And if one of them has no associated t->to_proc, the t->to_proc->inner_lock will not be acquired. This means that transaction accesses in binder_thread_release() after t->to_proc has been cleared might race with binder_free_transaction() and cause a use-after-free error as reported by KASAN: ================================================================== BUG: KASAN: slab-use-after-free in binder_thread_release+0x5d0/0x798 Write of size 8 at addr ffff000016627500 by task X/715 CPU: 17 UID: 0 PID: 715 Comm: X Not tainted 7.1.0-rc5-00149-g8fde5d1d47f6 #30 PREEMPT Hardware name: linux,dummy-virt (DT) Call trace: binder_thread_release+0x5d0/0x798 binder_ioctl+0x12c0/0x299c [...] Allocated by task 717 on cpu 18 at 67.267803s: __kasan_kmalloc+0xa0/0xbc __kmalloc_cache_noprof+0x174/0x444 binder_transaction+0x554/0x8150 binder_thread_write+0xa30/0x4354 binder_ioctl+0x20f0/0x299c [...] Freed by task 202 on cpu 18 at 90.416221s: __kasan_slab_free+0x58/0x80 kfree+0x1a0/0x4a4 binder_free_transaction+0x150/0x294 binder_send_failed_reply+0x398/0x6d8 binder_release_work+0x3e4/0x4ec binder_deferred_func+0xbd8/0x104c [...] ================================================================== In order to avoid this, make sure that binder_free_transaction() reads the t->to_proc under the transaction lock. This will serialize the transaction release with the accesses in binder_thread_release(). Plus, it matches the documented locking rules for @to_proc. Cc: stable Fixes: 7a4408c6bd3e ("binder: make sure accesses to proc/thread are safe") Reviewed-by: Alice Ryhl Signed-off-by: Carlos Llamas Link: https://patch.msgid.link/20260619185233.2194678-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman

binder: don't use %pK through printk

2026-03-04T12:20:35+00:00

[ 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 Acked-by: Carlos Llamas Reviewed-by: Alice Ryhl Link: https://patch.msgid.link/20260107-restricted-pointers-binder-v1-1-181018bf3812@linutronix.de Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

binder: fix BR_FROZEN_REPLY error log

2026-02-11T12:41:45+00:00

commit 1769f90e5ba2a6d24bb46b85da33fe861c68f005 upstream. The error logging for failed transactions is misleading as it always reports "dead process or thread" even when the target is actually frozen. Additionally, the pid and tid are reversed which can further confuse debugging efforts. Fix both issues. Cc: stable@kernel.org Cc: Steven Moreland Fixes: a15dac8b2286 ("binder: additional transaction error logs") Signed-off-by: Carlos Llamas Reviewed-by: Alice Ryhl Link: https://patch.msgid.link/20260123175702.2154348-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman

binder: fix UAF in binder_netlink_report()

2026-02-11T12:41:45+00:00

commit 5e8a3d01544282e50d887d76f30d1496a0a53562 upstream. Oneway transactions sent to frozen targets via binder_proc_transaction() return a BR_TRANSACTION_PENDING_FROZEN error but they are still treated as successful since the target is expected to thaw at some point. It is then not safe to access 't' after BR_TRANSACTION_PENDING_FROZEN errors as the transaction could have been consumed by the now thawed target. This is the case for binder_netlink_report() which derreferences 't' after a pending frozen error, as pointed out by the following KASAN report: ================================================================== BUG: KASAN: slab-use-after-free in binder_netlink_report.isra.0+0x694/0x6c8 Read of size 8 at addr ffff00000f98ba38 by task binder-util/522 CPU: 4 UID: 0 PID: 522 Comm: binder-util Not tainted 6.19.0-rc6-00015-gc03e9c42ae8f #1 PREEMPT Hardware name: linux,dummy-virt (DT) Call trace: binder_netlink_report.isra.0+0x694/0x6c8 binder_transaction+0x66e4/0x79b8 binder_thread_write+0xab4/0x4440 binder_ioctl+0x1fd4/0x2940 [...] Allocated by task 522: __kmalloc_cache_noprof+0x17c/0x50c binder_transaction+0x584/0x79b8 binder_thread_write+0xab4/0x4440 binder_ioctl+0x1fd4/0x2940 [...] Freed by task 488: kfree+0x1d0/0x420 binder_free_transaction+0x150/0x234 binder_thread_read+0x2d08/0x3ce4 binder_ioctl+0x488/0x2940 [...] ================================================================== Instead, make a transaction copy so the data can be safely accessed by binder_netlink_report() after a pending frozen error. While here, add a comment about not using t->buffer in binder_netlink_report(). Cc: stable@vger.kernel.org Fixes: 63740349eba7 ("binder: introduce transaction reports via netlink") Signed-off-by: Carlos Llamas Reviewed-by: Alice Ryhl Link: https://patch.msgid.link/20260122180203.1502637-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman

binder: remove "invalid inc weak" check

2025-10-22T06:04:15+00:00

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 Signed-off-by: Alice Ryhl Link: https://patch.msgid.link/20251015-binder-weak-inc-v1-1-7914b092c371@google.com Signed-off-by: Greg Kroah-Hartman

binder: Fix missing kernel-doc entries in binder.c

2025-10-13T09:08:25+00:00

Fix several kernel-doc warnings in `drivers/android/binder.c` caused by undocumented struct members and function parameters. In particular, add missing documentation for the `@thread` parameter in binder_free_buf_locked(). Signed-off-by: Kriish Sharma Acked-by: Carlos Llamas Signed-off-by: Greg Kroah-Hartman

binder: add tracepoint for netlink reports

2025-08-19T10:53:02+00:00

Add a tracepoint to capture the same details that are being sent through the generic netlink interface during transaction failures. This provides a useful debugging tool to observe the events independently from the netlink listeners. Signed-off-by: Carlos Llamas Link: https://lore.kernel.org/r/20250727182932.2499194-6-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman

binder: introduce transaction reports via netlink

2025-08-19T10:53:01+00:00

Introduce a generic netlink multicast event to report binder transaction failures to userspace. This allows subscribers to monitor these events and take appropriate actions, such as stopping a misbehaving application that is spamming a service with huge amount of transactions. The multicast event contains full details of the failed transactions, including the sender/target PIDs, payload size and specific error code. This interface is defined using a YAML spec, from which the UAPI and kernel headers and source are auto-generated. Signed-off-by: Li Li Signed-off-by: Carlos Llamas Link: https://lore.kernel.org/r/20250727182932.2499194-4-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman

binder: add t->is_async and t->is_reply

2025-08-19T10:53:01+00:00

Replace the t->need_reply flag with the more descriptive t->is_async and and t->is_reply flags. The 'need_reply' flag was only used for debugging purposes and the new flags can be used to distinguish between the type of transactions too: sync, async and reply. For now, only update the logging in print_binder_transaction_ilocked(). However, the new flags can be used in the future to replace the current patterns and improve readability. e.g.: - if (!reply && !(tr->flags & TF_ONE_WAY)) + if (t->is_async) This patch is in preparation for binder's generic netlink implementation and no functional changes are intended. Signed-off-by: Carlos Llamas Link: https://lore.kernel.org/r/20250727182932.2499194-3-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman