From dd9bc4f9f144a89d52a197fcf0ea033a287b7095 Mon Sep 17 00:00:00 2001 From: Martijn Coenen Date: Fri, 30 Sep 2016 14:10:07 +0200 Subject: [PATCH] android: binder: support for scatter-gather. Previously all data passed over binder needed to be serialized, with the exception of Binder objects and file descriptors. This patchs adds support for scatter-gathering raw memory buffers into a binder transaction, avoiding the need to first serialize them into a Parcel. To remain backwards compatibile with existing binder clients, it introduces two new command ioctls for this purpose - BC_TRANSACTION_SG and BC_REPLY_SG. These commands may only be used with the new binder_transaction_data_sg structure, which adds a field for the total size of the buffers we are scatter-gathering. Because memory buffers may contain pointers to other buffers, we allow callers to specify a parent buffer and an offset into it, to indicate this is a location pointing to the buffer that we are fixing up. The kernel will then take care of fixing up the pointer to that buffer as well. Change-Id: I02417f28cff14688f2e1d6fcb959438fd96566cc Signed-off-by: Martijn Coenen --- drivers/android/binder.c | 244 ++++++++++++++++++++++++++++++++++-- include/uapi/linux/android/binder.h | 45 +++++++ 2 files changed, 276 insertions(+), 13 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 83a6c1bbbad5..a0f4d29e5148 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -153,6 +153,9 @@ module_param_call(stop_on_user_error, binder_set_stop_on_user_error, #define to_binder_fd_object(hdr) container_of(hdr, struct binder_fd_object, hdr) +#define to_binder_buffer_object(hdr) \ + container_of(hdr, struct binder_buffer_object, hdr) + enum binder_stat_types { BINDER_STAT_PROC, BINDER_STAT_THREAD, @@ -166,7 +169,7 @@ enum binder_stat_types { struct binder_stats { int br[_IOC_NR(BR_FAILED_REPLY) + 1]; - int bc[_IOC_NR(BC_DEAD_BINDER_DONE) + 1]; + int bc[_IOC_NR(BC_REPLY_SG) + 1]; int obj_created[BINDER_STAT_COUNT]; int obj_deleted[BINDER_STAT_COUNT]; }; @@ -1306,6 +1309,9 @@ static size_t binder_validate_object(struct binder_buffer *buffer, u64 offset) case BINDER_TYPE_FD: object_size = sizeof(struct binder_fd_object); break; + case BINDER_TYPE_PTR: + object_size = sizeof(struct binder_buffer_object); + break; default: return 0; } @@ -1316,11 +1322,111 @@ static size_t binder_validate_object(struct binder_buffer *buffer, u64 offset) return 0; } +/** + * binder_validate_ptr() - validates binder_buffer_object in a binder_buffer. + * @b: binder_buffer containing the object + * @index: index in offset array at which the binder_buffer_object is + * located + * @start: points to the start of the offset array + * @num_valid: the number of valid offsets in the offset array + * + * Return: If @index is within the valid range of the offset array + * described by @start and @num_valid, and if there's a valid + * binder_buffer_object at the offset found in index @index + * of the offset array, that object is returned. Otherwise, + * %NULL is returned. + * Note that the offset found in index @index itself is not + * verified; this function assumes that @num_valid elements + * from @start were previously verified to have valid offsets. + */ +static struct binder_buffer_object *binder_validate_ptr(struct binder_buffer *b, + binder_size_t index, + binder_size_t *start, + binder_size_t num_valid) +{ + struct binder_buffer_object *buffer_obj; + binder_size_t *offp; + + if (index >= num_valid) + return NULL; + + offp = start + index; + buffer_obj = (struct binder_buffer_object *)(b->data + *offp); + if (buffer_obj->hdr.type != BINDER_TYPE_PTR) + return NULL; + + return buffer_obj; +} + +/** + * binder_validate_fixup() - validates pointer/fd fixups happen in order. + * @b: transaction buffer + * @objects_start start of objects buffer + * @buffer: binder_buffer_object in which to fix up + * @offset: start offset in @buffer to fix up + * @last_obj: last binder_buffer_object that we fixed up in + * @last_min_offset: minimum fixup offset in @last_obj + * + * Return: %true if a fixup in buffer @buffer at offset @offset is + * allowed. + * + * For safety reasons, we only allow fixups inside a buffer to happen + * at increasing offsets; additionally, we only allow fixup on the last + * buffer object that was verified, or one of its parents. + * + * Example of what is allowed: + * + * A + * B (parent = A, offset = 0) + * C (parent = A, offset = 16) + * D (parent = C, offset = 0) + * E (parent = A, offset = 32) // min_offset is 16 (C.parent_offset) + * + * Examples of what is not allowed: + * + * Decreasing offsets within the same parent: + * A + * C (parent = A, offset = 16) + * B (parent = A, offset = 0) // decreasing offset within A + * + * Referring to a parent that wasn't the last object or any of its parents: + * A + * B (parent = A, offset = 0) + * C (parent = A, offset = 0) + * C (parent = A, offset = 16) + * D (parent = B, offset = 0) // B is not A or any of A's parents + */ +static bool binder_validate_fixup(struct binder_buffer *b, + binder_size_t *objects_start, + struct binder_buffer_object *buffer, + binder_size_t fixup_offset, + struct binder_buffer_object *last_obj, + binder_size_t last_min_offset) +{ + if (!last_obj) { + /* Nothing to fix up in */ + return false; + } + + while (last_obj != buffer) { + /* + * Safe to retrieve the parent of last_obj, since it + * was already previously verified by the driver. + */ + if ((last_obj->flags & BINDER_BUFFER_FLAG_HAS_PARENT) == 0) + return false; + last_min_offset = last_obj->parent_offset + sizeof(uintptr_t); + last_obj = (struct binder_buffer_object *) + (b->data + *(objects_start + last_obj->parent)); + } + return (fixup_offset >= last_min_offset); +} + static void binder_transaction_buffer_release(struct binder_proc *proc, struct binder_buffer *buffer, binder_size_t *failed_at) { - binder_size_t *offp, *off_end; + binder_size_t *offp, *off_start, *off_end; int debug_id = buffer->debug_id; binder_debug(BINDER_DEBUG_TRANSACTION, @@ -1331,13 +1437,13 @@ static void binder_transaction_buffer_release(struct binder_proc *proc, if (buffer->target_node) binder_dec_node(buffer->target_node, 1, 0); - offp = (binder_size_t *)(buffer->data + - ALIGN(buffer->data_size, sizeof(void *))); + off_start = (binder_size_t *)(buffer->data + + ALIGN(buffer->data_size, sizeof(void *))); if (failed_at) off_end = failed_at; else - off_end = (void *)offp + buffer->offsets_size; - for (; offp < off_end; offp++) { + off_end = (void *)off_start + buffer->offsets_size; + for (offp = off_start; offp < off_end; offp++) { struct binder_object_header *hdr; size_t object_size = binder_validate_object(buffer, *offp); @@ -1393,7 +1499,12 @@ static void binder_transaction_buffer_release(struct binder_proc *proc, if (failed_at) task_close_fd(proc, fp->fd); } break; - + case BINDER_TYPE_PTR: + /* + * Nothing to do here, this will get cleaned up when the + * transaction buffer gets freed + */ + break; default: pr_err("transaction release %d bad object type %x\n", debug_id, hdr->type); @@ -1563,6 +1674,53 @@ err_fd_not_accepted: return ret; } +static int binder_fixup_parent(struct binder_transaction *t, + struct binder_thread *thread, + struct binder_buffer_object *bp, + binder_size_t *off_start, + binder_size_t num_valid, + struct binder_buffer_object *last_fixup_obj, + binder_size_t last_fixup_min_off) +{ + struct binder_buffer_object *parent; + u8 *parent_buffer; + struct binder_buffer *b = t->buffer; + struct binder_proc *proc = thread->proc; + struct binder_proc *target_proc = t->to_proc; + + if (!(bp->flags & BINDER_BUFFER_FLAG_HAS_PARENT)) + return 0; + + parent = binder_validate_ptr(b, bp->parent, off_start, num_valid); + if (!parent) { + binder_user_error("%d:%d got transaction with invalid parent offset or type\n", + proc->pid, thread->pid); + return -EINVAL; + } + + if (!binder_validate_fixup(b, off_start, + parent, bp->parent_offset, + last_fixup_obj, + last_fixup_min_off)) { + binder_user_error("%d:%d got transaction with out-of-order buffer fixup\n", + proc->pid, thread->pid); + return -EINVAL; + } + + if (parent->length < sizeof(binder_uintptr_t) || + bp->parent_offset > parent->length - sizeof(binder_uintptr_t)) { + /* No space for a pointer here! */ + binder_user_error("%d:%d got transaction with invalid parent offset\n", + proc->pid, thread->pid); + return -EINVAL; + } + parent_buffer = (u8 *)(parent->buffer - + target_proc->user_buffer_offset); + *(binder_uintptr_t *)(parent_buffer + bp->parent_offset) = bp->buffer; + + return 0; +} + static void binder_transaction(struct binder_proc *proc, struct binder_thread *thread, struct binder_transaction_data *tr, int reply, @@ -1571,8 +1729,9 @@ static void binder_transaction(struct binder_proc *proc, int ret; struct binder_transaction *t; struct binder_work *tcomplete; - binder_size_t *offp, *off_end; + binder_size_t *offp, *off_end, *off_start; binder_size_t off_min; + u8 *sg_bufp, *sg_buf_end; struct binder_proc *target_proc; struct binder_thread *target_thread = NULL; struct binder_node *target_node = NULL; @@ -1581,6 +1740,8 @@ static void binder_transaction(struct binder_proc *proc, struct binder_transaction *in_reply_to = NULL; struct binder_transaction_log_entry *e; uint32_t return_error; + struct binder_buffer_object *last_fixup_obj = NULL; + binder_size_t last_fixup_min_off = 0; struct binder_context *context = proc->context; e = binder_transaction_log_add(&binder_transaction_log); @@ -1755,8 +1916,9 @@ static void binder_transaction(struct binder_proc *proc, if (target_node) binder_inc_node(target_node, 1, 0, NULL); - offp = (binder_size_t *)(t->buffer->data + - ALIGN(tr->data_size, sizeof(void *))); + off_start = (binder_size_t *)(t->buffer->data + + ALIGN(tr->data_size, sizeof(void *))); + offp = off_start; if (copy_from_user(t->buffer->data, (const void __user *)(uintptr_t) tr->data.ptr.buffer, tr->data_size)) { @@ -1778,7 +1940,16 @@ static void binder_transaction(struct binder_proc *proc, return_error = BR_FAILED_REPLY; goto err_bad_offset; } - off_end = (void *)offp + tr->offsets_size; + if (!IS_ALIGNED(extra_buffers_size, sizeof(u64))) { + binder_user_error("%d:%d got transaction with unaligned buffers size, %lld\n", + proc->pid, thread->pid, + extra_buffers_size); + return_error = BR_FAILED_REPLY; + goto err_bad_offset; + } + off_end = (void *)off_start + tr->offsets_size; + sg_bufp = (u8 *)(PTR_ALIGN(off_end, sizeof(void *))); + sg_buf_end = sg_bufp + extra_buffers_size; off_min = 0; for (; offp < off_end; offp++) { struct binder_object_header *hdr; @@ -1831,7 +2002,41 @@ static void binder_transaction(struct binder_proc *proc, fp->pad_binder = 0; fp->fd = target_fd; } break; - + case BINDER_TYPE_PTR: { + struct binder_buffer_object *bp = + to_binder_buffer_object(hdr); + size_t buf_left = sg_buf_end - sg_bufp; + + if (bp->length > buf_left) { + binder_user_error("%d:%d got transaction with too large buffer\n", + proc->pid, thread->pid); + return_error = BR_FAILED_REPLY; + goto err_bad_offset; + } + if (copy_from_user(sg_bufp, + (const void __user *)(uintptr_t) + bp->buffer, bp->length)) { + binder_user_error("%d:%d got transaction with invalid offsets ptr\n", + proc->pid, thread->pid); + return_error = BR_FAILED_REPLY; + goto err_copy_data_failed; + } + /* Fixup buffer pointer to target proc address space */ + bp->buffer = (uintptr_t)sg_bufp + + target_proc->user_buffer_offset; + sg_bufp += ALIGN(bp->length, sizeof(u64)); + + ret = binder_fixup_parent(t, thread, bp, off_start, + offp - off_start, + last_fixup_obj, + last_fixup_min_off); + if (ret < 0) { + return_error = BR_FAILED_REPLY; + goto err_translate_failed; + } + last_fixup_obj = bp; + last_fixup_min_off = 0; + } break; default: binder_user_error("%d:%d got transaction with invalid object type, %x\n", proc->pid, thread->pid, hdr->type); @@ -2085,6 +2290,17 @@ static int binder_thread_write(struct binder_proc *proc, break; } + case BC_TRANSACTION_SG: + case BC_REPLY_SG: { + struct binder_transaction_data_sg tr; + + if (copy_from_user(&tr, ptr, sizeof(tr))) + return -EFAULT; + ptr += sizeof(tr); + binder_transaction(proc, thread, &tr.transaction_data, + cmd == BC_REPLY_SG, tr.buffers_size); + break; + } case BC_TRANSACTION: case BC_REPLY: { struct binder_transaction_data tr; @@ -3606,7 +3822,9 @@ static const char * const binder_command_strings[] = { "BC_EXIT_LOOPER", "BC_REQUEST_DEATH_NOTIFICATION", "BC_CLEAR_DEATH_NOTIFICATION", - "BC_DEAD_BINDER_DONE" + "BC_DEAD_BINDER_DONE", + "BC_TRANSACTION_SG", + "BC_REPLY_SG", }; static const char * const binder_objstat_strings[] = { diff --git a/include/uapi/linux/android/binder.h b/include/uapi/linux/android/binder.h index f67c2b1c0713..f3ef6e2634ba 100644 --- a/include/uapi/linux/android/binder.h +++ b/include/uapi/linux/android/binder.h @@ -33,6 +33,7 @@ enum { BINDER_TYPE_HANDLE = B_PACK_CHARS('s', 'h', '*', B_TYPE_LARGE), BINDER_TYPE_WEAK_HANDLE = B_PACK_CHARS('w', 'h', '*', B_TYPE_LARGE), BINDER_TYPE_FD = B_PACK_CHARS('f', 'd', '*', B_TYPE_LARGE), + BINDER_TYPE_PTR = B_PACK_CHARS('p', 't', '*', B_TYPE_LARGE), }; enum { @@ -95,6 +96,39 @@ struct binder_fd_object { binder_uintptr_t cookie; }; + +/* struct binder_buffer_object - object describing a userspace buffer + * @hdr: common header structure + * @flags: one or more BINDER_BUFFER_* flags + * @buffer: address of the buffer + * @length: length of the buffer + * @parent: index in offset array pointing to parent buffer + * @parent_offset: offset in @parent pointing to this buffer + * + * A binder_buffer object represents an object that the + * binder kernel driver can copy verbatim to the target + * address space. A buffer itself may be pointed to from + * within another buffer, meaning that the pointer inside + * that other buffer needs to be fixed up as well. This + * can be done by setting the BINDER_BUFFER_FLAG_HAS_PARENT + * flag in @flags, by setting @parent buffer to the index + * in the offset array pointing to the parent binder_buffer_object, + * and by setting @parent_offset to the offset in the parent buffer + * at which the pointer to this buffer is located. + */ +struct binder_buffer_object { + struct binder_object_header hdr; + __u32 flags; + binder_uintptr_t buffer; + binder_size_t length; + binder_size_t parent; + binder_size_t parent_offset; +}; + +enum { + BINDER_BUFFER_FLAG_HAS_PARENT = 0x01, +}; + /* * On 64-bit platforms where user code may run in 32-bits the driver must * translate the buffer (and local binder) addresses appropriately. @@ -187,6 +221,11 @@ struct binder_transaction_data { } data; }; +struct binder_transaction_data_sg { + struct binder_transaction_data transaction_data; + binder_size_t buffers_size; +}; + struct binder_ptr_cookie { binder_uintptr_t ptr; binder_uintptr_t cookie; @@ -371,6 +410,12 @@ enum binder_driver_command_protocol { /* * void *: cookie */ + + BC_TRANSACTION_SG = _IOW('c', 17, struct binder_transaction_data_sg), + BC_REPLY_SG = _IOW('c', 18, struct binder_transaction_data_sg), + /* + * binder_transaction_data_sg: the sent command. + */ }; #endif /* _UAPI_LINUX_BINDER_H */ -- 2.11.0