The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 0fa53349c3acba0239369ba4cd133740a408d246 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023052832-ideally-gleeful-6ac6@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: 0fa53349c3ac ("binder: add lockless binder_alloc_(set|get)_vma()") c0fd2101781e ("Revert "android: binder: stop saving a pointer to the VMA"") b15655b12ddc ("Revert "binder_alloc: add missing mmap_lock calls when using the VMA"") 7b0dbd940765 ("binder: fix binder_alloc kernel-doc warnings") d6d04d71daae ("binder: remove binder_alloc_set_vma()") e66b77e50522 ("binder: rename alloc->vma_vm_mm to alloc->mm") 50e177c5bfd9 ("Merge 6.0-rc4 into char-misc-next") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 0fa53349c3acba0239369ba4cd133740a408d246 Mon Sep 17 00:00:00 2001 From: Carlos Llamas <cmllamas@xxxxxxxxxx> Date: Tue, 2 May 2023 20:12:19 +0000 Subject: [PATCH] binder: add lockless binder_alloc_(set|get)_vma() Bring back the original lockless design in binder_alloc to determine whether the buffer setup has been completed by the ->mmap() handler. However, this time use smp_load_acquire() and smp_store_release() to wrap all the ordering in a single macro call. Also, add comments to make it evident that binder uses alloc->vma to determine when the binder_alloc has been fully initialized. In these scenarios acquiring the mmap_lock is not required. Fixes: a43cfc87caaf ("android: binder: stop saving a pointer to the VMA") Cc: Liam Howlett <liam.howlett@xxxxxxxxxx> Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx> Link: https://lore.kernel.org/r/20230502201220.1756319-3-cmllamas@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index eb082b33115b..e7c9d466f8e8 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -309,17 +309,18 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, return vma ? -ENOMEM : -ESRCH; } +static inline void binder_alloc_set_vma(struct binder_alloc *alloc, + struct vm_area_struct *vma) +{ + /* pairs with smp_load_acquire in binder_alloc_get_vma() */ + smp_store_release(&alloc->vma, vma); +} + static inline struct vm_area_struct *binder_alloc_get_vma( struct binder_alloc *alloc) { - struct vm_area_struct *vma = NULL; - - if (alloc->vma) { - /* Look at description in binder_alloc_set_vma */ - smp_rmb(); - vma = alloc->vma; - } - return vma; + /* pairs with smp_store_release in binder_alloc_set_vma() */ + return smp_load_acquire(&alloc->vma); } static bool debug_low_async_space_locked(struct binder_alloc *alloc, int pid) @@ -382,6 +383,7 @@ static struct binder_buffer *binder_alloc_new_buf_locked( size_t size, data_offsets_size; int ret; + /* Check binder_alloc is fully initialized */ if (!binder_alloc_get_vma(alloc)) { binder_alloc_debug(BINDER_DEBUG_USER_ERROR, "%d: binder_alloc_buf, no vma\n", @@ -777,7 +779,9 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc, buffer->free = 1; binder_insert_free_buffer(alloc, buffer); alloc->free_async_space = alloc->buffer_size / 2; - alloc->vma = vma; + + /* Signal binder_alloc is fully initialized */ + binder_alloc_set_vma(alloc, vma); return 0; @@ -959,7 +963,7 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc) */ void binder_alloc_vma_close(struct binder_alloc *alloc) { - alloc->vma = 0; + binder_alloc_set_vma(alloc, NULL); } /**
