summaryrefslogtreecommitdiff
path: root/drivers/android/binder_alloc.c
diff options
context:
space:
mode:
authorTodd Kjos <tkjos@android.com>2019-02-08 21:35:14 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-02-12 12:43:57 +0300
commit1a7c3d9bb7a926e88d5f57643e75ad1abfc55013 (patch)
treea64c869735ee00eded6f495cb250afefd96e1bba /drivers/android/binder_alloc.c
parent6cffd79504ce040f460831030d3069fa1c99bb71 (diff)
downloadlinux-1a7c3d9bb7a926e88d5f57643e75ad1abfc55013.tar.xz
binder: create userspace-to-binder-buffer copy function
The binder driver uses a vm_area to map the per-process binder buffer space. For 32-bit android devices, this is now taking too much vmalloc space. This patch removes the use of vm_area when copying the transaction data from the sender to the buffer space. Instead of using copy_from_user() for multi-page copies, it now uses binder_alloc_copy_user_to_buffer() which uses kmap() and kunmap() to map each page, and uses copy_from_user() for copying to that page. Signed-off-by: Todd Kjos <tkjos@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android/binder_alloc.c')
-rw-r--r--drivers/android/binder_alloc.c113
1 files changed, 113 insertions, 0 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 022cd80e80cc..94c0d85c4e75 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -29,6 +29,8 @@
#include <linux/list_lru.h>
#include <linux/ratelimit.h>
#include <asm/cacheflush.h>
+#include <linux/uaccess.h>
+#include <linux/highmem.h>
#include "binder_alloc.h"
#include "binder_trace.h"
@@ -1053,3 +1055,114 @@ int binder_alloc_shrinker_init(void)
}
return ret;
}
+
+/**
+ * check_buffer() - verify that buffer/offset is safe to access
+ * @alloc: binder_alloc for this proc
+ * @buffer: binder buffer to be accessed
+ * @offset: offset into @buffer data
+ * @bytes: bytes to access from offset
+ *
+ * Check that the @offset/@bytes are within the size of the given
+ * @buffer and that the buffer is currently active and not freeable.
+ * Offsets must also be multiples of sizeof(u32). The kernel is
+ * allowed to touch the buffer in two cases:
+ *
+ * 1) when the buffer is being created:
+ * (buffer->free == 0 && buffer->allow_user_free == 0)
+ * 2) when the buffer is being torn down:
+ * (buffer->free == 0 && buffer->transaction == NULL).
+ *
+ * Return: true if the buffer is safe to access
+ */
+static inline bool check_buffer(struct binder_alloc *alloc,
+ struct binder_buffer *buffer,
+ binder_size_t offset, size_t bytes)
+{
+ size_t buffer_size = binder_alloc_buffer_size(alloc, buffer);
+
+ return buffer_size >= bytes &&
+ offset <= buffer_size - bytes &&
+ IS_ALIGNED(offset, sizeof(u32)) &&
+ !buffer->free &&
+ (!buffer->allow_user_free || !buffer->transaction);
+}
+
+/**
+ * binder_alloc_get_page() - get kernel pointer for given buffer offset
+ * @alloc: binder_alloc for this proc
+ * @buffer: binder buffer to be accessed
+ * @buffer_offset: offset into @buffer data
+ * @pgoffp: address to copy final page offset to
+ *
+ * Lookup the struct page corresponding to the address
+ * at @buffer_offset into @buffer->data. If @pgoffp is not
+ * NULL, the byte-offset into the page is written there.
+ *
+ * The caller is responsible to ensure that the offset points
+ * to a valid address within the @buffer and that @buffer is
+ * not freeable by the user. Since it can't be freed, we are
+ * guaranteed that the corresponding elements of @alloc->pages[]
+ * cannot change.
+ *
+ * Return: struct page
+ */
+static struct page *binder_alloc_get_page(struct binder_alloc *alloc,
+ struct binder_buffer *buffer,
+ binder_size_t buffer_offset,
+ pgoff_t *pgoffp)
+{
+ binder_size_t buffer_space_offset = buffer_offset +
+ (buffer->data - alloc->buffer);
+ pgoff_t pgoff = buffer_space_offset & ~PAGE_MASK;
+ size_t index = buffer_space_offset >> PAGE_SHIFT;
+ struct binder_lru_page *lru_page;
+
+ lru_page = &alloc->pages[index];
+ *pgoffp = pgoff;
+ return lru_page->page_ptr;
+}
+
+/**
+ * binder_alloc_copy_user_to_buffer() - copy src user to tgt user
+ * @alloc: binder_alloc for this proc
+ * @buffer: binder buffer to be accessed
+ * @buffer_offset: offset into @buffer data
+ * @from: userspace pointer to source buffer
+ * @bytes: bytes to copy
+ *
+ * Copy bytes from source userspace to target buffer.
+ *
+ * Return: bytes remaining to be copied
+ */
+unsigned long
+binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc,
+ struct binder_buffer *buffer,
+ binder_size_t buffer_offset,
+ const void __user *from,
+ size_t bytes)
+{
+ if (!check_buffer(alloc, buffer, buffer_offset, bytes))
+ return bytes;
+
+ while (bytes) {
+ unsigned long size;
+ unsigned long ret;
+ struct page *page;
+ pgoff_t pgoff;
+ void *kptr;
+
+ page = binder_alloc_get_page(alloc, buffer,
+ buffer_offset, &pgoff);
+ size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
+ kptr = kmap(page) + pgoff;
+ ret = copy_from_user(kptr, from, size);
+ kunmap(page);
+ if (ret)
+ return bytes - size + ret;
+ bytes -= size;
+ from += size;
+ buffer_offset += size;
+ }
+ return 0;
+}