This is a note to let you know that I've just added the patch titled android: binder: stop saving a pointer to the VMA to the 5.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: android-binder-stop-saving-a-pointer-to-the-vma.patch and it can be found in the queue-5.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit c4259947d12a36a35a02bb284ec1e0a676c503b2 Author: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Date: Mon Jun 20 21:09:09 2022 -0400 android: binder: stop saving a pointer to the VMA [ 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@xxxxxxxxxxxxxxxxxxxx: 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@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Hridya Valsaraju <hridya@xxxxxxxxxx> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> Cc: Martijn Coenen <maco@xxxxxxxxxxx> Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx> Cc: Todd Kjos <tkjos@xxxxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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);