kernel/linux.git/drivers/android/binder_internal.h, branch v5.15.7

binder: use euid from cred instead of using task

2021-11-12T14:05:48+00:00

commit 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b upstream. Save the 'struct cred' associated with a binder process at initial open to avoid potential race conditions when converting to an euid. Set a transaction's sender_euid from the 'struct cred' saved at binder_open() instead of looking up the euid from the binder proc's 'struct task'. This ensures the euid is associated with the security context that of the task that opened binder. Cc: stable@vger.kernel.org # 4.4+ Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") Signed-off-by: Todd Kjos Suggested-by: Stephen Smalley Suggested-by: Jann Horn Acked-by: Casey Schaufler Signed-off-by: Paul Moore Signed-off-by: Greg Kroah-Hartman

binder: fix freeze race

2021-09-14T06:46:08+00:00

Currently cgroup freezer is used to freeze the application threads, and BINDER_FREEZE is used to freeze the corresponding binder interface. There's already a mechanism in ioctl(BINDER_FREEZE) to wait for any existing transactions to drain out before actually freezing the binder interface. But freezing an app requires 2 steps, freezing the binder interface with ioctl(BINDER_FREEZE) and then freezing the application main threads with cgroupfs. This is not an atomic operation. The following race issue might happen. 1) Binder interface is frozen by ioctl(BINDER_FREEZE); 2) Main thread A initiates a new sync binder transaction to process B; 3) Main thread A is frozen by "echo 1 > cgroup.freeze"; 4) The response from process B reaches the frozen thread, which will unexpectedly fail. This patch provides a mechanism to check if there's any new pending transaction happening between ioctl(BINDER_FREEZE) and freezing the main thread. If there's any, the main thread freezing operation can be rolled back to finish the pending transaction. Furthermore, the response might reach the binder driver before the rollback actually happens. That will still cause failed transaction. As the other process doesn't wait for another response of the response, the response transaction failure can be fixed by treating the response transaction like an oneway/async one, allowing it to reach the frozen thread. And it will be consumed when the thread gets unfrozen later. NOTE: This patch reuses the existing definition of struct binder_frozen_status_info but expands the bit assignments of __u32 member sync_recv. To ensure backward compatibility, bit 0 of sync_recv still indicates there's an outstanding sync binder transaction. This patch adds new information to bit 1 of sync_recv, indicating the binder transaction happens exactly when there's a race. If an existing userspace app runs on a new kernel, a sync binder call will set bit 0 of sync_recv so ioctl(BINDER_GET_FROZEN_INFO) still return the expected value (true). The app just doesn't check bit 1 intentionally so it doesn't have the ability to tell if there's a race. This behavior is aligned with what happens on an old kernel which doesn't set bit 1 at all. A new userspace app can 1) check bit 0 to know if there's a sync binder transaction happened when being frozen - same as before; and 2) check bit 1 to know if that sync binder transaction happened exactly when there's a race - a new information for rollback decision. the same time, confirmed the pending transactions succeeded. Fixes: 432ff1e91694 ("binder: BINDER_FREEZE ioctl") Acked-by: Todd Kjos Cc: stable Signed-off-by: Li Li Test: stress test with apps being frozen and initiating binder calls at Link: https://lore.kernel.org/r/20210910164210.2282716-2-dualli@chromium.org Signed-off-by: Greg Kroah-Hartman

binder: tell userspace to dump current backtrace when detected oneway spamming

2021-04-10T08:52:04+00:00

When async binder buffer got exhausted, some normal oneway transactions will also be discarded and may cause system or application failures. By that time, the binder debug information we dump may not be relevant to the root cause. And this issue is difficult to debug if without the backtrace of the thread sending spam. This change will send BR_ONEWAY_SPAM_SUSPECT to userspace when oneway spamming is detected, request to dump current backtrace. Oneway spamming will be reported only once when exceeding the threshold (target process dips below 80% of its oneway space, and current process is responsible for either more than 50 transactions, or more than 50% of the oneway space). And the detection will restart when the async buffer has returned to a healthy state. Acked-by: Todd Kjos Signed-off-by: Hang Lu Link: https://lore.kernel.org/r/1617961246-4502-3-git-send-email-hangl@codeaurora.org Signed-off-by: Greg Kroah-Hartman

binder: fix the missing BR_FROZEN_REPLY in binder_return_strings

2021-04-10T08:52:04+00:00

Add BR_FROZEN_REPLY in binder_return_strings to support stat function. Fixes: ae28c1be1e54 ("binder: BINDER_GET_FROZEN_INFO ioctl") Acked-by: Todd Kjos Signed-off-by: Hang Lu Link: https://lore.kernel.org/r/1617961246-4502-2-git-send-email-hangl@codeaurora.org Signed-off-by: Greg Kroah-Hartman

binder: BINDER_GET_FROZEN_INFO ioctl

2021-03-24T07:26:31+00:00

User space needs to know if binder transactions occurred to frozen processes. Introduce a new BINDER_GET_FROZEN ioctl and keep track of transactions occurring to frozen proceses. Signed-off-by: Marco Ballesio Signed-off-by: Li Li Acked-by: Todd Kjos Link: https://lore.kernel.org/r/20210316011630.1121213-4-dualli@chromium.org Signed-off-by: Greg Kroah-Hartman

binder: BINDER_FREEZE ioctl

2021-03-24T07:26:31+00:00

Frozen tasks can't process binder transactions, so a way is required to inform transmitting ends of communication failures due to the frozen state of their receiving counterparts. Additionally, races are possible between transitions to frozen state and binder transactions enqueued to a specific process. Implement BINDER_FREEZE ioctl for user space to inform the binder driver about the intention to freeze or unfreeze a process. When the ioctl is called, block the caller until any pending binder transactions toward the target process are flushed. Return an error to transactions to processes marked as frozen. Co-developed-by: Todd Kjos Acked-by: Todd Kjos Signed-off-by: Marco Ballesio Signed-off-by: Todd Kjos Signed-off-by: Li Li Link: https://lore.kernel.org/r/20210316011630.1121213-2-dualli@chromium.org Signed-off-by: Greg Kroah-Hartman

binder: move structs from core file to header file

2020-11-11T07:20:34+00:00

Moving all structs to header file makes module more extendable, and makes all these structs to be defined in the same file. Signed-off-by: Frankie.Chang Acked-by: Todd Kjos Link: https://lore.kernel.org/r/1605063764-12930-2-git-send-email-Frankie.Chang@mediatek.com Signed-off-by: Greg Kroah-Hartman

binder: prevent UAF for binderfs devices II

2020-03-03T18:58:37+00:00

This is a necessary follow up to the first fix I proposed and we merged in 2669b8b0c79 ("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 51d8a7eca677 ("binder: prevent UAF read in print_binder_transaction_log_entry()"). Fixes: 3ad20fe393b3 ("binder: implement binderfs") Fixes: 2669b8b0c798 ("binder: prevent UAF for binderfs devices") Fixes: 03e2e07e3814 ("binder: Make transaction_log available in binderfs") Related : 51d8a7eca677 ("binder: prevent UAF read in print_binder_transaction_log_entry()") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner Acked-by: Todd Kjos Link: https://lore.kernel.org/r/20200303164340.670054-1-christian.brauner@ubuntu.com Signed-off-by: Greg Kroah-Hartman

binder: prevent UAF for binderfs devices

2020-03-03T07:02:57+00:00

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 51d8a7eca677 ("binder: prevent UAF read in print_binder_transaction_log_entry()"). Fixes: 3ad20fe393b3 ("binder: implement binderfs") Fixes: 03e2e07e3814 ("binder: Make transaction_log available in binderfs") Related : 51d8a7eca677 ("binder: prevent UAF read in print_binder_transaction_log_entry()") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner Acked-by: Todd Kjos Signed-off-by: Greg Kroah-Hartman

binder: prevent UAF read in print_binder_transaction_log_entry()

2019-10-10T12:39:22+00:00

When a binder transaction is initiated on a binder device coming from a binderfs instance, a pointer to the name of the binder device is stashed in the binder_transaction_log_entry's context_name member. Later on it is used to print the name in print_binder_transaction_log_entry(). By the time print_binder_transaction_log_entry() accesses context_name binderfs_evict_inode() might have already freed the associated memory thereby causing a UAF. Do the simple thing and prevent this by copying the name of the binder device instead of stashing a pointer to it. Reported-by: Jann Horn Fixes: 03e2e07e3814 ("binder: Make transaction_log available in binderfs") Link: https://lore.kernel.org/r/CAG48ez14Q0-F8LqsvcNbyR2o6gPW8SHXsm4u5jmD9MpsteM2Tw@mail.gmail.com Signed-off-by: Christian Brauner Reviewed-by: Joel Fernandes (Google) Acked-by: Todd Kjos Reviewed-by: Hridya Valsaraju Link: https://lore.kernel.org/r/20191008130159.10161-1-christian.brauner@ubuntu.com Signed-off-by: Greg Kroah-Hartman