From a0e44c64b6061dda7e00b7c458e4523e2331b739 Mon Sep 17 00:00:00 2001 From: Carlos Llamas Date: Mon, 1 Aug 2022 18:25:11 +0000 Subject: binder: fix UAF of ref->proc caused by race condition A transaction of type BINDER_TYPE_WEAK_HANDLE can fail to increment the reference for a node. In this case, the target proc normally releases the failed reference upon close as expected. However, if the target is dying in parallel the call will race with binder_deferred_release(), so the target could have released all of its references by now leaving the cleanup of the new failed reference unhandled. The transaction then ends and the target proc gets released making the ref->proc now a dangling pointer. Later on, ref->node is closed and we attempt to take spin_lock(&ref->proc->inner_lock), which leads to the use-after-free bug reported below. Let's fix this by cleaning up the failed reference on the spot instead of relying on the target to do so. ================================================================== BUG: KASAN: use-after-free in _raw_spin_lock+0xa8/0x150 Write of size 4 at addr ffff5ca207094238 by task kworker/1:0/590 CPU: 1 PID: 590 Comm: kworker/1:0 Not tainted 5.19.0-rc8 #10 Hardware name: linux,dummy-virt (DT) Workqueue: events binder_deferred_func Call trace: dump_backtrace.part.0+0x1d0/0x1e0 show_stack+0x18/0x70 dump_stack_lvl+0x68/0x84 print_report+0x2e4/0x61c kasan_report+0xa4/0x110 kasan_check_range+0xfc/0x1a4 __kasan_check_write+0x3c/0x50 _raw_spin_lock+0xa8/0x150 binder_deferred_func+0x5e0/0x9b0 process_one_work+0x38c/0x5f0 worker_thread+0x9c/0x694 kthread+0x188/0x190 ret_from_fork+0x10/0x20 Acked-by: Christian Brauner (Microsoft) Signed-off-by: Carlos Llamas Cc: stable # 4.14+ Link: https://lore.kernel.org/r/20220801182511.3371447-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'drivers/android') diff --git a/drivers/android/binder.c b/drivers/android/binder.c index c964d7c8c384..6428f6be69e3 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -1385,6 +1385,18 @@ static int binder_inc_ref_for_node(struct binder_proc *proc, } ret = binder_inc_ref_olocked(ref, strong, target_list); *rdata = ref->data; + if (ret && ref == new_ref) { + /* + * Cleanup the failed reference here as the target + * could now be dead and have already released its + * references by now. Calling on the new reference + * with strong=0 and a tmp_refs will not decrement + * the node. The new_ref gets kfree'd below. + */ + binder_cleanup_ref_olocked(new_ref); + ref = NULL; + } + binder_proc_unlock(proc); if (new_ref && ref != new_ref) /* -- cgit v1.2.3 From d6f35446d0769a98e9d761593d267cdd24f09ecd Mon Sep 17 00:00:00 2001 From: Liam Howlett Date: Wed, 10 Aug 2022 16:02:25 +0000 Subject: binder_alloc: Add missing mmap_lock calls when using the VMA Take the mmap_read_lock() when using the VMA in binder_alloc_print_pages() and when checking for a VMA in binder_alloc_new_buf_locked(). It is worth noting binder_alloc_new_buf_locked() drops the VMA read lock after it verifies a VMA exists, but may be taken again deeper in the call stack, if necessary. Fixes: a43cfc87caaf (android: binder: stop saving a pointer to the VMA) Cc: stable Reported-by: Ondrej Mosnacek Reported-by: syzbot+a7b60a176ec13cafb793@syzkaller.appspotmail.com Tested-by: Ondrej Mosnacek Acked-by: Carlos Llamas Signed-off-by: Liam R. Howlett Link: https://lore.kernel.org/r/20220810160209.1630707-1-Liam.Howlett@oracle.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) (limited to 'drivers/android') diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 1014beb12802..51f4e1c5cd01 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -402,12 +402,15 @@ static struct binder_buffer *binder_alloc_new_buf_locked( size_t size, data_offsets_size; int ret; + mmap_read_lock(alloc->vma_vm_mm); if (!binder_alloc_get_vma(alloc)) { + mmap_read_unlock(alloc->vma_vm_mm); binder_alloc_debug(BINDER_DEBUG_USER_ERROR, "%d: binder_alloc_buf, no vma\n", alloc->pid); return ERR_PTR(-ESRCH); } + mmap_read_unlock(alloc->vma_vm_mm); data_offsets_size = ALIGN(data_size, sizeof(void *)) + ALIGN(offsets_size, sizeof(void *)); @@ -929,17 +932,25 @@ void binder_alloc_print_pages(struct seq_file *m, * Make sure the binder_alloc is fully initialized, otherwise we might * read inconsistent state. */ - if (binder_alloc_get_vma(alloc) != NULL) { - for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) { - page = &alloc->pages[i]; - if (!page->page_ptr) - free++; - else if (list_empty(&page->lru)) - active++; - else - lru++; - } + + mmap_read_lock(alloc->vma_vm_mm); + if (binder_alloc_get_vma(alloc) == NULL) { + mmap_read_unlock(alloc->vma_vm_mm); + goto uninitialized; } + + mmap_read_unlock(alloc->vma_vm_mm); + for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) { + page = &alloc->pages[i]; + if (!page->page_ptr) + free++; + else if (list_empty(&page->lru)) + active++; + else + lru++; + } + +uninitialized: mutex_unlock(&alloc->mutex); seq_printf(m, " pages: %d:%d:%d\n", active, lru, free); seq_printf(m, " pages high watermark: %zu\n", alloc->pages_high); -- cgit v1.2.3 From db7e5c10351e3dd58e6bef237c8fa74282e5d59e Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Fri, 19 Aug 2022 10:55:54 +0200 Subject: Revert "binder_alloc: Add missing mmap_lock calls when using the VMA" This reverts commit d6f35446d0769a98e9d761593d267cdd24f09ecd. It is coming in through Andrew's tree instead, and for some reason we have different versions. I trust the version from Andrew more as the original offending commit came through his tree. Fixes: d6f35446d076 ("binder_alloc: Add missing mmap_lock calls when using the VMA") Cc: stable Cc: Ondrej Mosnacek Cc: Ondrej Mosnacek Cc: Carlos Llamas Cc: Liam R. Howlett Reported-by: Stephen Rothwell Link: https://lore.kernel.org/r/20220819184027.7b3fda3e@canb.auug.org.au Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 31 ++++++++++--------------------- 1 file changed, 10 insertions(+), 21 deletions(-) (limited to 'drivers/android') diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 51f4e1c5cd01..1014beb12802 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -402,15 +402,12 @@ static struct binder_buffer *binder_alloc_new_buf_locked( size_t size, data_offsets_size; int ret; - mmap_read_lock(alloc->vma_vm_mm); if (!binder_alloc_get_vma(alloc)) { - mmap_read_unlock(alloc->vma_vm_mm); binder_alloc_debug(BINDER_DEBUG_USER_ERROR, "%d: binder_alloc_buf, no vma\n", alloc->pid); return ERR_PTR(-ESRCH); } - mmap_read_unlock(alloc->vma_vm_mm); data_offsets_size = ALIGN(data_size, sizeof(void *)) + ALIGN(offsets_size, sizeof(void *)); @@ -932,25 +929,17 @@ void binder_alloc_print_pages(struct seq_file *m, * Make sure the binder_alloc is fully initialized, otherwise we might * read inconsistent state. */ - - mmap_read_lock(alloc->vma_vm_mm); - if (binder_alloc_get_vma(alloc) == NULL) { - mmap_read_unlock(alloc->vma_vm_mm); - goto uninitialized; - } - - mmap_read_unlock(alloc->vma_vm_mm); - for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) { - page = &alloc->pages[i]; - if (!page->page_ptr) - free++; - else if (list_empty(&page->lru)) - active++; - else - lru++; + if (binder_alloc_get_vma(alloc) != NULL) { + for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) { + page = &alloc->pages[i]; + if (!page->page_ptr) + free++; + else if (list_empty(&page->lru)) + active++; + else + lru++; + } } - -uninitialized: mutex_unlock(&alloc->mutex); seq_printf(m, " pages: %d:%d:%d\n", active, lru, free); seq_printf(m, " pages high watermark: %zu\n", alloc->pages_high); -- cgit v1.2.3 From 1da52815d5f1b654c89044db0cdc6adce43da1f1 Mon Sep 17 00:00:00 2001 From: Carlos Llamas Date: Mon, 29 Aug 2022 20:12:48 +0000 Subject: binder: fix alloc->vma_vm_mm null-ptr dereference Syzbot reported a couple issues introduced by commit 44e602b4e52f ("binder_alloc: add missing mmap_lock calls when using the VMA"), in which we attempt to acquire the mmap_lock when alloc->vma_vm_mm has not been initialized yet. This can happen if a binder_proc receives a transaction without having previously called mmap() to setup the binder_proc->alloc space in [1]. Also, a similar issue occurs via binder_alloc_print_pages() when we try to dump the debugfs binder stats file in [2]. Sample of syzbot's crash report: ================================================================== KASAN: null-ptr-deref in range [0x0000000000000128-0x000000000000012f] CPU: 0 PID: 3755 Comm: syz-executor229 Not tainted 6.0.0-rc1-next-20220819-syzkaller #0 syz-executor229[3755] cmdline: ./syz-executor2294415195 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 RIP: 0010:__lock_acquire+0xd83/0x56d0 kernel/locking/lockdep.c:4923 [...] Call Trace: lock_acquire kernel/locking/lockdep.c:5666 [inline] lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 down_read+0x98/0x450 kernel/locking/rwsem.c:1499 mmap_read_lock include/linux/mmap_lock.h:117 [inline] binder_alloc_new_buf_locked drivers/android/binder_alloc.c:405 [inline] binder_alloc_new_buf+0xa5/0x19e0 drivers/android/binder_alloc.c:593 binder_transaction+0x242e/0x9a80 drivers/android/binder.c:3199 binder_thread_write+0x664/0x3220 drivers/android/binder.c:3986 binder_ioctl_write_read drivers/android/binder.c:5036 [inline] binder_ioctl+0x3470/0x6d00 drivers/android/binder.c:5323 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] ================================================================== Fix these issues by setting up alloc->vma_vm_mm pointer during open() and caching directly from current->mm. This guarantees we have a valid reference to take the mmap_lock during scenarios described above. [1] https://syzkaller.appspot.com/bug?extid=f7dc54e5be28950ac459 [2] https://syzkaller.appspot.com/bug?extid=a75ebe0452711c9e56d9 Fixes: 44e602b4e52f ("binder_alloc: add missing mmap_lock calls when using the VMA") Cc: # v5.15+ Cc: Liam R. Howlett Reported-by: syzbot+f7dc54e5be28950ac459@syzkaller.appspotmail.com Reported-by: syzbot+a75ebe0452711c9e56d9@syzkaller.appspotmail.com Reviewed-by: Liam R. Howlett Acked-by: Todd Kjos Signed-off-by: Carlos Llamas Link: https://lore.kernel.org/r/20220829201254.1814484-2-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/android') diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 1014beb12802..a61df6e1103a 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -322,7 +322,6 @@ static inline void binder_alloc_set_vma(struct binder_alloc *alloc, */ if (vma) { vm_start = vma->vm_start; - alloc->vma_vm_mm = vma->vm_mm; mmap_assert_write_locked(alloc->vma_vm_mm); } else { mmap_assert_locked(alloc->vma_vm_mm); @@ -792,7 +791,6 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, binder_insert_free_buffer(alloc, buffer); alloc->free_async_space = alloc->buffer_size / 2; binder_alloc_set_vma(alloc, vma); - mmgrab(alloc->vma_vm_mm); return 0; @@ -1080,6 +1078,8 @@ static struct shrinker binder_shrinker = { void binder_alloc_init(struct binder_alloc *alloc) { alloc->pid = current->group_leader->pid; + alloc->vma_vm_mm = current->mm; + mmgrab(alloc->vma_vm_mm); mutex_init(&alloc->mutex); INIT_LIST_HEAD(&alloc->buffers); } -- cgit v1.2.3