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Subject[PATCH v2 4/7] binder: avoid kernel vm_area for buffer fixups
Date
Refactor the functions to validate and fixup struct
binder_buffer pointer objects to avoid using vm_area
pointers. Instead copy to/from kernel space using
binder_alloc_copy_to_buffer() and
binder_alloc_copy_from_buffer(). The following
functions were refactored:

binder_validate_ptr()
binder_validate_fixup()
binder_fixup_parent()

Signed-off-by: Todd Kjos <tkjos@google.com>
---
drivers/android/binder.c | 146 ++++++++++++++++++++++++++-------------
1 file changed, 97 insertions(+), 49 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 8063b405e4fa..98163bf5f35c 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2092,10 +2092,13 @@ static size_t binder_get_object(struct binder_proc *proc,

/**
* binder_validate_ptr() - validates binder_buffer_object in a binder_buffer.
+ * @proc: binder_proc owning the buffer
* @b: binder_buffer containing the object
+ * @object: struct binder_object to read into
* @index: index in offset array at which the binder_buffer_object is
* located
- * @start: points to the start of the offset array
+ * @start_offset: points to the start of the offset array
+ * @object_offsetp: offset of @object read from @b
* @num_valid: the number of valid offsets in the offset array
*
* Return: If @index is within the valid range of the offset array
@@ -2106,34 +2109,46 @@ static size_t binder_get_object(struct binder_proc *proc,
* 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.
+ * If @object_offsetp is non-NULL, then the offset within
+ * @b is written to it.
*/
-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)
+static struct binder_buffer_object *binder_validate_ptr(
+ struct binder_proc *proc,
+ struct binder_buffer *b,
+ struct binder_object *object,
+ binder_size_t index,
+ binder_size_t start_offset,
+ binder_size_t *object_offsetp,
+ binder_size_t num_valid)
{
- struct binder_buffer_object *buffer_obj;
- binder_size_t *offp;
+ size_t object_size;
+ binder_size_t object_offset;
+ unsigned long buffer_offset;

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)
+ buffer_offset = start_offset + sizeof(binder_size_t) * index;
+ binder_alloc_copy_from_buffer(&proc->alloc, &object_offset,
+ b, buffer_offset, sizeof(object_offset));
+ object_size = binder_get_object(proc, b, object_offset, object);
+ if (!object_size || object->hdr.type != BINDER_TYPE_PTR)
return NULL;
+ if (object_offsetp)
+ *object_offsetp = object_offset;

- return buffer_obj;
+ return &object->bbo;
}

/**
* binder_validate_fixup() - validates pointer/fd fixups happen in order.
+ * @proc: binder_proc owning the buffer
* @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
+ * @objects_start_offset: offset to start of objects buffer
+ * @buffer_obj_offset: offset to binder_buffer_object in which to fix up
+ * @fixup_offset: start offset in @buffer to fix up
+ * @last_obj_offset: offset to last binder_buffer_object that we fixed
+ * @last_min_offset: minimum fixup offset in object at @last_obj_offset
*
* Return: %true if a fixup in buffer @buffer at offset @offset is
* allowed.
@@ -2164,28 +2179,41 @@ static struct binder_buffer_object *binder_validate_ptr(struct binder_buffer *b,
* 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,
+static bool binder_validate_fixup(struct binder_proc *proc,
+ struct binder_buffer *b,
+ binder_size_t objects_start_offset,
+ binder_size_t buffer_obj_offset,
binder_size_t fixup_offset,
- struct binder_buffer_object *last_obj,
+ binder_size_t last_obj_offset,
binder_size_t last_min_offset)
{
- if (!last_obj) {
+ if (!last_obj_offset) {
/* Nothing to fix up in */
return false;
}

- while (last_obj != buffer) {
+ while (last_obj_offset != buffer_obj_offset) {
+ unsigned long buffer_offset;
+ struct binder_object last_object;
+ struct binder_buffer_object *last_bbo;
+ size_t object_size = binder_get_object(proc, b, last_obj_offset,
+ &last_object);
+ if (object_size != sizeof(*last_bbo))
+ return false;
+
+ last_bbo = &last_object.bbo;
/*
* 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)
+ if ((last_bbo->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));
+ last_min_offset = last_bbo->parent_offset + sizeof(uintptr_t);
+ buffer_offset = objects_start_offset +
+ sizeof(binder_size_t) * last_bbo->parent,
+ binder_alloc_copy_from_buffer(&proc->alloc, &last_obj_offset,
+ b, buffer_offset,
+ sizeof(last_obj_offset));
}
return (fixup_offset >= last_min_offset);
}
@@ -2254,6 +2282,7 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
{
binder_size_t *offp, *off_start, *off_end;
int debug_id = buffer->debug_id;
+ binder_size_t off_start_offset;

binder_debug(BINDER_DEBUG_TRANSACTION,
"%d buffer release %d, size %zd-%zd, failed at %pK\n",
@@ -2263,8 +2292,8 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
if (buffer->target_node)
binder_dec_node(buffer->target_node, 1, 0);

- off_start = (binder_size_t *)(buffer->data +
- ALIGN(buffer->data_size, sizeof(void *)));
+ off_start_offset = ALIGN(buffer->data_size, sizeof(void *));
+ off_start = (binder_size_t *)(buffer->data + off_start_offset);
if (failed_at)
off_end = failed_at;
else
@@ -2350,6 +2379,7 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
case BINDER_TYPE_FDA: {
struct binder_fd_array_object *fda;
struct binder_buffer_object *parent;
+ struct binder_object ptr_object;
uintptr_t parent_buffer;
u32 *fd_array;
size_t fd_index;
@@ -2365,8 +2395,10 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
}

fda = to_binder_fd_array_object(hdr);
- parent = binder_validate_ptr(buffer, fda->parent,
- off_start,
+ parent = binder_validate_ptr(proc, buffer, &ptr_object,
+ fda->parent,
+ off_start_offset,
+ NULL,
offp - off_start);
if (!parent) {
pr_err("transaction release %d bad parent offset\n",
@@ -2665,9 +2697,9 @@ static int binder_translate_fd_array(struct binder_fd_array_object *fda,
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 off_start_offset,
binder_size_t num_valid,
- struct binder_buffer_object *last_fixup_obj,
+ binder_size_t last_fixup_obj_off,
binder_size_t last_fixup_min_off)
{
struct binder_buffer_object *parent;
@@ -2675,20 +2707,25 @@ static int binder_fixup_parent(struct binder_transaction *t,
struct binder_buffer *b = t->buffer;
struct binder_proc *proc = thread->proc;
struct binder_proc *target_proc = t->to_proc;
+ struct binder_object object;
+ binder_size_t buffer_offset;
+ binder_size_t parent_offset;

if (!(bp->flags & BINDER_BUFFER_FLAG_HAS_PARENT))
return 0;

- parent = binder_validate_ptr(b, bp->parent, off_start, num_valid);
+ parent = binder_validate_ptr(target_proc, b, &object, bp->parent,
+ off_start_offset, &parent_offset,
+ 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,
+ if (!binder_validate_fixup(target_proc, b, off_start_offset,
+ parent_offset, bp->parent_offset,
+ last_fixup_obj_off,
last_fixup_min_off)) {
binder_user_error("%d:%d got transaction with out-of-order buffer fixup\n",
proc->pid, thread->pid);
@@ -2705,7 +2742,10 @@ static int binder_fixup_parent(struct binder_transaction *t,
parent_buffer = (u8 *)((uintptr_t)parent->buffer -
binder_alloc_get_user_buffer_offset(
&target_proc->alloc));
- *(binder_uintptr_t *)(parent_buffer + bp->parent_offset) = bp->buffer;
+ buffer_offset = bp->parent_offset +
+ (uintptr_t)parent_buffer - (uintptr_t)b->data;
+ binder_alloc_copy_to_buffer(&target_proc->alloc, b, buffer_offset,
+ &bp->buffer, sizeof(bp->buffer));

return 0;
}
@@ -2825,6 +2865,7 @@ static void binder_transaction(struct binder_proc *proc,
struct binder_work *w;
struct binder_work *tcomplete;
binder_size_t *offp, *off_end, *off_start;
+ binder_size_t off_start_offset;
binder_size_t off_min;
u8 *sg_bufp, *sg_buf_end;
struct binder_proc *target_proc = NULL;
@@ -2835,7 +2876,7 @@ static void binder_transaction(struct binder_proc *proc,
uint32_t return_error = 0;
uint32_t return_error_param = 0;
uint32_t return_error_line = 0;
- struct binder_buffer_object *last_fixup_obj = NULL;
+ binder_size_t last_fixup_obj_off = 0;
binder_size_t last_fixup_min_off = 0;
struct binder_context *context = proc->context;
int t_debug_id = atomic_inc_return(&binder_last_id);
@@ -3132,8 +3173,8 @@ static void binder_transaction(struct binder_proc *proc,
t->buffer->transaction = t;
t->buffer->target_node = target_node;
trace_binder_transaction_alloc_buf(t->buffer);
- off_start = (binder_size_t *)(t->buffer->data +
- ALIGN(tr->data_size, sizeof(void *)));
+ off_start_offset = ALIGN(tr->data_size, sizeof(void *));
+ off_start = (binder_size_t *)(t->buffer->data + off_start_offset);
offp = off_start;

if (binder_alloc_copy_user_to_buffer(
@@ -3266,11 +3307,15 @@ static void binder_transaction(struct binder_proc *proc,
fp, sizeof(*fp));
} break;
case BINDER_TYPE_FDA: {
+ struct binder_object ptr_object;
+ binder_size_t parent_offset;
struct binder_fd_array_object *fda =
to_binder_fd_array_object(hdr);
struct binder_buffer_object *parent =
- binder_validate_ptr(t->buffer, fda->parent,
- off_start,
+ binder_validate_ptr(target_proc, t->buffer,
+ &ptr_object, fda->parent,
+ off_start_offset,
+ &parent_offset,
offp - off_start);
if (!parent) {
binder_user_error("%d:%d got transaction with invalid parent offset or type\n",
@@ -3280,9 +3325,11 @@ static void binder_transaction(struct binder_proc *proc,
return_error_line = __LINE__;
goto err_bad_parent;
}
- if (!binder_validate_fixup(t->buffer, off_start,
- parent, fda->parent_offset,
- last_fixup_obj,
+ if (!binder_validate_fixup(target_proc, t->buffer,
+ off_start_offset,
+ parent_offset,
+ fda->parent_offset,
+ last_fixup_obj_off,
last_fixup_min_off)) {
binder_user_error("%d:%d got transaction with out-of-order buffer fixup\n",
proc->pid, thread->pid);
@@ -3299,7 +3346,7 @@ static void binder_transaction(struct binder_proc *proc,
return_error_line = __LINE__;
goto err_translate_failed;
}
- last_fixup_obj = parent;
+ last_fixup_obj_off = parent_offset;
last_fixup_min_off =
fda->parent_offset + sizeof(u32) * fda->num_fds;
} break;
@@ -3338,9 +3385,10 @@ static void binder_transaction(struct binder_proc *proc,
&target_proc->alloc);
sg_bufp += ALIGN(bp->length, sizeof(u64));

- ret = binder_fixup_parent(t, thread, bp, off_start,
+ ret = binder_fixup_parent(t, thread, bp,
+ off_start_offset,
offp - off_start,
- last_fixup_obj,
+ last_fixup_obj_off,
last_fixup_min_off);
if (ret < 0) {
return_error = BR_FAILED_REPLY;
@@ -3351,7 +3399,7 @@ static void binder_transaction(struct binder_proc *proc,
binder_alloc_copy_to_buffer(&target_proc->alloc,
t->buffer, object_offset,
bp, sizeof(*bp));
- last_fixup_obj = t->buffer->data + object_offset;
+ last_fixup_obj_off = object_offset;
last_fixup_min_off = 0;
} break;
default:
--
2.20.1.495.gaa96b0ce6b-goog
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