From: Liam R. Howlett Liam.Howlett@oracle.com
[ Upstream commit a43cfc87caaf46710c8027a8c23b8a55f1078f19 ]
Do not record a pointer to a VMA outside of the mmap_lock for later use. This is unsafe and there are a number of failure paths *after* the recorded VMA pointer may be freed during setup. There is no callback to the driver to clear the saved pointer from generic mm code. Furthermore, the VMA pointer may become stale if any number of VMA operations end up freeing the VMA so saving it was fragile to being with.
Instead, change the binder_alloc struct to record the start address of the VMA and use vma_lookup() to get the vma when needed. Add lockdep mmap_lock checks on updates to the vma pointer to ensure the lock is held and depend on that lock for synchronization of readers and writers - which was already the case anyways, so the smp_wmb()/smp_rmb() was not necessary.
[akpm@linux-foundation.org: fix drivers/android/binder_alloc_selftest.c] Link: https://lkml.kernel.org/r/20220621140212.vpkio64idahetbyf@revolver Fixes: da1b9564e85b ("android: binder: fix the race mmap and alloc_new_buf_locked") Reported-by: syzbot+58b51ac2b04e388ab7b0@syzkaller.appspotmail.com Signed-off-by: Liam R. Howlett Liam.Howlett@oracle.com Cc: Minchan Kim minchan@kernel.org Cc: Christian Brauner (Microsoft) brauner@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Hridya Valsaraju hridya@google.com Cc: Joel Fernandes joel@joelfernandes.org Cc: Martijn Coenen maco@android.com Cc: Suren Baghdasaryan surenb@google.com Cc: Todd Kjos tkjos@android.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/android/binder_alloc.c | 30 ++++++++++++------------- drivers/android/binder_alloc.h | 2 +- drivers/android/binder_alloc_selftest.c | 2 +- 3 files changed, 16 insertions(+), 18 deletions(-)
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 2ac1008a5f39..a93a7d2a8caf 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -213,7 +213,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
if (mm) { mmap_read_lock(mm); - vma = alloc->vma; + vma = vma_lookup(mm, alloc->vma_addr); }
if (!vma && need_mm) { @@ -313,16 +313,15 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, static inline void binder_alloc_set_vma(struct binder_alloc *alloc, struct vm_area_struct *vma) { - if (vma) + unsigned long vm_start = 0; + + if (vma) { + vm_start = vma->vm_start; alloc->vma_vm_mm = vma->vm_mm; - /* - * If we see alloc->vma is not NULL, buffer data structures set up - * completely. Look at smp_rmb side binder_alloc_get_vma. - * We also want to guarantee new alloc->vma_vm_mm is always visible - * if alloc->vma is set. - */ - smp_wmb(); - alloc->vma = vma; + } + + mmap_assert_write_locked(alloc->vma_vm_mm); + alloc->vma_addr = vm_start; }
static inline struct vm_area_struct *binder_alloc_get_vma( @@ -330,11 +329,9 @@ static inline struct vm_area_struct *binder_alloc_get_vma( { struct vm_area_struct *vma = NULL;
- if (alloc->vma) { - /* Look at description in binder_alloc_set_vma */ - smp_rmb(); - vma = alloc->vma; - } + if (alloc->vma_addr) + vma = vma_lookup(alloc->vma_vm_mm, alloc->vma_addr); + return vma; }
@@ -817,7 +814,8 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc)
buffers = 0; mutex_lock(&alloc->mutex); - BUG_ON(alloc->vma); + BUG_ON(alloc->vma_addr && + vma_lookup(alloc->vma_vm_mm, alloc->vma_addr));
while ((n = rb_first(&alloc->allocated_buffers))) { buffer = rb_entry(n, struct binder_buffer, rb_node); diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h index 7dea57a84c79..1e4fd37af5e0 100644 --- a/drivers/android/binder_alloc.h +++ b/drivers/android/binder_alloc.h @@ -100,7 +100,7 @@ struct binder_lru_page { */ struct binder_alloc { struct mutex mutex; - struct vm_area_struct *vma; + unsigned long vma_addr; struct mm_struct *vma_vm_mm; void __user *buffer; struct list_head buffers; diff --git a/drivers/android/binder_alloc_selftest.c b/drivers/android/binder_alloc_selftest.c index c2b323bc3b3a..43a881073a42 100644 --- a/drivers/android/binder_alloc_selftest.c +++ b/drivers/android/binder_alloc_selftest.c @@ -287,7 +287,7 @@ void binder_selftest_alloc(struct binder_alloc *alloc) if (!binder_selftest_run) return; mutex_lock(&binder_selftest_lock); - if (!binder_selftest_run || !alloc->vma) + if (!binder_selftest_run || !alloc->vma_addr) goto done; pr_info("STARTED\n"); binder_selftest_alloc_offset(alloc, end_offset, 0);