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Rust Binder contains the following unsafe operation:
// SAFETY: A `NodeDeath` is never inserted into the death list
// of any node other than its owner, so it is either in this
// death list or in no death list.
unsafe { node_inner.death_list.remove(self) };
This operation is unsafe because when touching the prev/next pointers of
a list element, we have to ensure that no other thread is also touching
them in parallel. If the node is present in the list that `remove` is
called on, then that is fine because we have exclusive access to that
list. If the node is not in any list, then it's also ok. But if it's
present in a different list that may be accessed in parallel, then that
may be a data race on the prev/next pointers.
And unfortunately that is exactly what is happening here. In
Node::release, we:
1. Take the lock.
2. Move all items to a local list on the stack.
3. Drop the lock.
4. Iterate the local list on the stack.
Combined with threads using the unsafe remove method on the original
list, this leads to memory corruption of the prev/next pointers. This
leads to crashes like this one:
Unable to handle kernel paging request at virtual address 000bb9841bcac70e
Mem abort info:
ESR = 0x0000000096000044
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x04: level 0 translation fault
Data abort info:
ISV = 0, ISS = 0x00000044, ISS2 = 0x00000000
CM = 0, WnR = 1, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[000bb9841bcac70e] address between user and kernel address ranges
Internal error: Oops: 0000000096000044 [#1] PREEMPT SMP
google-cdd 538c004.gcdd: context saved(CPU:1)
item - log_kevents is disabled
Modules linked in: ... rust_binder
CPU: 1 UID: 0 PID: 2092 Comm: kworker/1:178 Tainted: G S W OE 6.12.52-android16-5-g98debd5df505-4k #1 f94a6367396c5488d635708e43ee0c888d230b0b
Tainted: [S]=CPU_OUT_OF_SPEC, [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: MUSTANG PVT 1.0 based on LGA (DT)
Workqueue: events _RNvXs6_NtCsdfZWD8DztAw_6kernel9workqueueINtNtNtB7_4sync3arc3ArcNtNtCs8QPsHWIn21X_16rust_binder_main7process7ProcessEINtB5_15WorkItemPointerKy0_E3runB13_ [rust_binder]
pstate: 23400005 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : _RNvXs3_NtCs8QPsHWIn21X_16rust_binder_main7processNtB5_7ProcessNtNtCsdfZWD8DztAw_6kernel9workqueue8WorkItem3run+0x450/0x11f8 [rust_binder]
lr : _RNvXs3_NtCs8QPsHWIn21X_16rust_binder_main7processNtB5_7ProcessNtNtCsdfZWD8DztAw_6kernel9workqueue8WorkItem3run+0x464/0x11f8 [rust_binder]
sp : ffffffc09b433ac0
x29: ffffffc09b433d30 x28: ffffff8821690000 x27: ffffffd40cbaa448
x26: ffffff8821690000 x25: 00000000ffffffff x24: ffffff88d0376578
x23: 0000000000000001 x22: ffffffc09b433c78 x21: ffffff88e8f9bf40
x20: ffffff88e8f9bf40 x19: ffffff882692b000 x18: ffffffd40f10bf00
x17: 00000000c006287d x16: 00000000c006287d x15: 00000000000003b0
x14: 0000000000000100 x13: 000000201cb79ae0 x12: fffffffffffffff0
x11: 0000000000000000 x10: 0000000000000001 x9 : 0000000000000000
x8 : b80bb9841bcac706 x7 : 0000000000000001 x6 : fffffffebee63f30
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000004c31 x1 : ffffff88216900c0 x0 : ffffff88e8f9bf00
Call trace:
_RNvXs3_NtCs8QPsHWIn21X_16rust_binder_main7processNtB5_7ProcessNtNtCsdfZWD8DztAw_6kernel9workqueue8WorkItem3run+0x450/0x11f8 [rust_binder bbc172b53665bbc815363b22e97e3f7e3fe971fc]
process_scheduled_works+0x1c4/0x45c
worker_thread+0x32c/0x3e8
kthread+0x11c/0x1c8
ret_from_fork+0x10/0x20
Code: 94218d85 b4000155 a94026a8 d10102a0 (f9000509)
---[ end trace 0000000000000000 ]---
Thus, modify Node::release to pop items directly off the original list.
Cc: stable@vger.kernel.org
Fixes: eafedbc7c0 ("rust_binder: add Rust Binder driver")
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://patch.msgid.link/20251111-binder-fix-list-remove-v1-1-8ed14a0da63d@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.