linux/drivers/android/binder.c, branch v5.0

binderfs: remove separate device_initcall()

2019-02-01T14:50:26Z

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

binder: fix CONFIG_ANDROID_BINDER_DEVICES

2019-01-30T14:21:01Z

Several users have tried to only rely on binderfs to provide binder devices and set CONFIG_ANDROID_BINDER_DEVICES="" empty. This is a great use-case of binderfs and one that was always intended to work. However, this is currently not possible since setting CONFIG_ANDROID_BINDER_DEVICES="" emtpy will simply panic the kernel: kobject: (00000000028c2f79): attempted to be registered with empty name! WARNING: CPU: 7 PID: 1703 at lib/kobject.c:228 kobject_add_internal+0x288/0x2b0 Modules linked in: binder_linux(+) bridge stp llc ipmi_ssif gpio_ich dcdbas coretemp kvm_intel kvm irqbypass serio_raw input_leds lpc_ich i5100_edac mac_hid ipmi_si ipmi_devintf ipmi_msghandler sch_fq_codel ib_i CPU: 7 PID: 1703 Comm: modprobe Not tainted 5.0.0-rc2-brauner-binderfs #263 Hardware name: Dell DCS XS24-SC2 /XS24-SC2 , BIOS S59_3C20 04/07/2011 RIP: 0010:kobject_add_internal+0x288/0x2b0 Code: 12 95 48 c7 c7 78 63 3b 95 e8 77 35 71 ff e9 91 fe ff ff 0f 0b eb a7 0f 0b eb 9a 48 89 de 48 c7 c7 00 63 3b 95 e8 f8 95 6a ff <0f> 0b 41 bc ea ff ff ff e9 6d fe ff ff 41 bc fe ff ff ff e9 62 fe RSP: 0018:ffff973f84237a30 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffff8b53e2472010 RCX: 0000000000000006 RDX: 0000000000000007 RSI: 0000000000000086 RDI: ffff8b53edbd63a0 RBP: ffff973f84237a60 R08: 0000000000000342 R09: 0000000000000004 R10: ffff973f84237af0 R11: 0000000000000001 R12: 0000000000000000 R13: ffff8b53e9f1a1e0 R14: 00000000e9f1a1e0 R15: 0000000000a00037 FS: 00007fbac36f7540(0000) GS:ffff8b53edbc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fbac364cfa7 CR3: 00000004a6d48000 CR4: 00000000000406e0 Call Trace: kobject_add+0x71/0xd0 ? _cond_resched+0x19/0x40 ? mutex_lock+0x12/0x40 device_add+0x12e/0x6b0 device_create_groups_vargs+0xe4/0xf0 device_create_with_groups+0x3f/0x60 ? _cond_resched+0x19/0x40 misc_register+0x140/0x180 binder_init+0x1ed/0x2d4 [binder_linux] ? trace_event_define_fields_binder_transaction_fd_send+0x8e/0x8e [binder_linux] do_one_initcall+0x4a/0x1c9 ? _cond_resched+0x19/0x40 ? kmem_cache_alloc_trace+0x151/0x1c0 do_init_module+0x5f/0x216 load_module+0x223d/0x2b20 __do_sys_finit_module+0xfc/0x120 ? __do_sys_finit_module+0xfc/0x120 __x64_sys_finit_module+0x1a/0x20 do_syscall_64+0x5a/0x120 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fbac3202839 Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 1f f6 2c 00 f7 d8 64 89 01 48 RSP: 002b:00007ffd1494a908 EFLAGS: 00000246 ORIG_RAX: 0000000000000139 RAX: ffffffffffffffda RBX: 000055b629ebec60 RCX: 00007fbac3202839 RDX: 0000000000000000 RSI: 000055b629c20d2e RDI: 0000000000000003 RBP: 000055b629c20d2e R08: 0000000000000000 R09: 000055b629ec2310 R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000 R13: 000055b629ebed70 R14: 0000000000040000 R15: 000055b629ebec60 So check for the empty string since strsep() will otherwise return the emtpy string which will cause kobject_add_internal() to panic when trying to add a kobject with an emtpy name. Fixes: ac4812c5ffbb ("binder: Support multiple /dev instances") Cc: Martijn Coenen Signed-off-by: Christian Brauner Acked-by: Todd Kjos Signed-off-by: Greg Kroah-Hartman

binder: implement binderfs

2018-12-19T08:40:13Z

As discussed at Linux Plumbers Conference 2018 in Vancouver [1] this is the implementation of binderfs. /* Abstract */ binderfs is a backwards-compatible filesystem for Android's binder ipc mechanism. Each ipc namespace will mount a new binderfs instance. Mounting binderfs multiple times at different locations in the same ipc namespace will not cause a new super block to be allocated and hence it will be the same filesystem instance. Each new binderfs mount will have its own set of binder devices only visible in the ipc namespace it has been mounted in. All devices in a new binderfs mount will follow the scheme binder%d and numbering will always start at 0. /* Backwards compatibility */ Devices requested in the Kconfig via CONFIG_ANDROID_BINDER_DEVICES for the initial ipc namespace will work as before. They will be registered via misc_register() and appear in the devtmpfs mount. Specifically, the standard devices binder, hwbinder, and vndbinder will all appear in their standard locations in /dev. Mounting or unmounting the binderfs mount in the initial ipc namespace will have no effect on these devices, i.e. they will neither show up in the binderfs mount nor will they disappear when the binderfs mount is gone. /* binder-control */ Each new binderfs instance comes with a binder-control device. No other devices will be present at first. The binder-control device can be used to dynamically allocate binder devices. All requests operate on the binderfs mount the binder-control device resides in. Assuming a new instance of binderfs has been mounted at /dev/binderfs via mount -t binderfs binderfs /dev/binderfs. Then a request to create a new binder device can be made as illustrated in [2]. Binderfs devices can simply be removed via unlink(). /* Implementation details */ - dynamic major number allocation: When binderfs is registered as a new filesystem it will dynamically allocate a new major number. The allocated major number will be returned in struct binderfs_device when a new binder device is allocated. - global minor number tracking: Minor are tracked in a global idr struct that is capped at BINDERFS_MAX_MINOR. The minor number tracker is protected by a global mutex. This is the only point of contention between binderfs mounts. - struct binderfs_info: Each binderfs super block has its own struct binderfs_info that tracks specific details about a binderfs instance: - ipc namespace - dentry of the binder-control device - root uid and root gid of the user namespace the binderfs instance was mounted in - mountable by user namespace root: binderfs can be mounted by user namespace root in a non-initial user namespace. The devices will be owned by user namespace root. - binderfs binder devices without misc infrastructure: New binder devices associated with a binderfs mount do not use the full misc_register() infrastructure. The misc_register() infrastructure can only create new devices in the host's devtmpfs mount. binderfs does however only make devices appear under its own mountpoint and thus allocates new character device nodes from the inode of the root dentry of the super block. This will have the side-effect that binderfs specific device nodes do not appear in sysfs. This behavior is similar to devpts allocated pts devices and has no effect on the functionality of the ipc mechanism itself. [1]: https://goo.gl/JL2tfX [2]: program to allocate a new binderfs binder device: #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include int main(int argc, char *argv[]) { int fd, ret, saved_errno; size_t len; struct binderfs_device device = { 0 }; if (argc < 2) exit(EXIT_FAILURE); len = strlen(argv[1]); if (len > BINDERFS_MAX_NAME) exit(EXIT_FAILURE); memcpy(device.name, argv[1], len); fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC); if (fd < 0) { printf("%s - Failed to open binder-control device\n", strerror(errno)); exit(EXIT_FAILURE); } ret = ioctl(fd, BINDER_CTL_ADD, &device); saved_errno = errno; close(fd); errno = saved_errno; if (ret < 0) { printf("%s - Failed to allocate new binder device\n", strerror(errno)); exit(EXIT_FAILURE); } printf("Allocated new binder device with major %d, minor %d, and " "name %s\n", device.major, device.minor, device.name); exit(EXIT_SUCCESS); } Cc: Martijn Coenen Cc: Greg Kroah-Hartman Signed-off-by: Christian Brauner Acked-by: Todd Kjos Signed-off-by: Greg Kroah-Hartman

binder: fix use-after-free due to ksys_close() during fdget()

2018-12-19T08:40:13Z

44d8047f1d8 ("binder: use standard functions to allocate fds") exposed a pre-existing issue in the binder driver. fdget() is used in ksys_ioctl() as a performance optimization. One of the rules associated with fdget() is that ksys_close() must not be called between the fdget() and the fdput(). There is a case where this requirement is not met in the binder driver which results in the reference count dropping to 0 when the device is still in use. This can result in use-after-free or other issues. If userpace has passed a file-descriptor for the binder driver using a BINDER_TYPE_FDA object, then kys_close() is called on it when handling a binder_ioctl(BC_FREE_BUFFER) command. This violates the assumptions for using fdget(). The problem is fixed by deferring the close using task_work_add(). A new variant of __close_fd() was created that returns a struct file with a reference. The fput() is deferred instead of using ksys_close(). Fixes: 44d8047f1d87a ("binder: use standard functions to allocate fds") Suggested-by: Al Viro Signed-off-by: Todd Kjos Cc: stable Signed-off-by: Greg Kroah-Hartman

binder: filter out nodes when showing binder procs

2018-12-06T14:44:14Z

When dumping out binder transactions via a debug node, the output is too verbose if a process has many nodes. Change the output for transaction dumps to only display nodes with pending async transactions. Signed-off-by: Todd Kjos Signed-off-by: Greg Kroah-Hartman

binder: remove BINDER_DEBUG_ENTRY()

2018-12-06T14:42:18Z

We already have the DEFINE_SHOW_ATTRIBUTE.There is no need to define such a macro,so remove BINDER_DEBUG_ENTRY. Signed-off-by: Yangtao Li Acked-by: Todd Kjos Reviewed-by: Joey Pabalinas Signed-off-by: Greg Kroah-Hartman

Merge 4.20-rc5 into char-misc-next

2018-12-03T06:56:15Z

We need the fixes in here as well. Signed-off-by: Greg Kroah-Hartman

binder: fix sparse warnings on locking context

2018-11-26T19:12:05Z

Add __acquire()/__release() annnotations to fix warnings in sparse context checking There is one case where the warning was due to a lack of a "default:" case in a switch statement where a lock was being released in each of the cases, so the default case was added. Signed-off-by: Todd Kjos Signed-off-by: Greg Kroah-Hartman

binder: fix race that allows malicious free of live buffer

2018-11-26T19:01:47Z

Malicious code can attempt to free buffers using the BC_FREE_BUFFER ioctl to binder. There are protections against a user freeing a buffer while in use by the kernel, however there was a window where BC_FREE_BUFFER could be used to free a recently allocated buffer that was not completely initialized. This resulted in a use-after-free detected by KASAN with a malicious test program. This window is closed by setting the buffer's allow_user_free attribute to 0 when the buffer is allocated or when the user has previously freed it instead of waiting for the caller to set it. The problem was that when the struct buffer was recycled, allow_user_free was stale and set to 1 allowing a free to go through. Signed-off-by: Todd Kjos Acked-by: Arve Hjønnevåg Cc: stable # 4.14 Signed-off-by: Greg Kroah-Hartman

binder: make symbol 'binder_free_buf' static

2018-10-02T22:53:53Z

Fixes the following sparse warning: drivers/android/binder.c:3312:1: warning: symbol 'binder_free_buf' was not declared. Should it be static? Signed-off-by: Wei Yongjun Signed-off-by: Greg Kroah-Hartman