fuse_sideload: Change the minimal block size to 4096.

run_fuse_sideload() is passing the block size as the max_read
option, so it will only handle a request that involves at most two
blocks at a time. However, the minimal allowed value was set to 1024
prior to this CL, which is inconsistent with the kernel code
(fs/fuse/inode.c) that sets it to the greater of 4096 and the passed-in
max_read option. This would fail the calls with a block size / max_read
less than 4096 due to the wrongly computed block indices.

Note that we didn't observe real issue in practice, because we have been
using 64 KiB block sizes for both of adb and sdcard sideload calls. The
issue only shows up in my local CL (to come later) that uses 1024 block
size in run_fuse_sideload() tests.

Test: recovery_component_test
Test: adb sideload with the new recovery image on angler
Change-Id: Id9f0cfea13d0d193dcb7cd41a1553a23739545f2

Android.mk

@@ -25,7 +25,9 @@ LOCAL_SRC_FILES := fuse_sideload.cpp
 LOCAL_CFLAGS := -Wall -Werror
 LOCAL_CFLAGS += -D_XOPEN_SOURCE -D_GNU_SOURCE
 LOCAL_MODULE := libfusesideload
-LOCAL_STATIC_LIBRARIES := libcrypto
+LOCAL_STATIC_LIBRARIES := \
+    libcrypto \
+    libbase
 include $(BUILD_STATIC_LIBRARY)
 
 # libmounts (static library)

fuse_sideload.cpp

@@ -61,6 +61,9 @@
 #include <sys/uio.h>
 #include <unistd.h>
 
+#include <string>
+
+#include <android-base/stringprintf.h>
 #include <openssl/sha.h>
 
 #include "fuse_sideload.h"
@@ -364,16 +367,14 @@ static int handle_read(void* data, struct fuse_data* fd, const struct fuse_in_he
     return NO_STATUS;
 }
 
-int run_fuse_sideload(struct provider_vtab* vtab, void* cookie,
-                      uint64_t file_size, uint32_t block_size)
-{
-    int result;
-
-    // If something's already mounted on our mountpoint, try to remove
-    // it.  (Mostly in case of a previous abnormal exit.)
+int run_fuse_sideload(struct provider_vtab* vtab, void* cookie, uint64_t file_size,
+                      uint32_t block_size) {
+  // If something's already mounted on our mountpoint, try to remove it. (Mostly in case of a
+  // previous abnormal exit.)
   umount2(FUSE_SIDELOAD_HOST_MOUNTPOINT, MNT_FORCE);
 
-    if (block_size < 1024) {
+  // fs/fuse/inode.c in kernel code uses the greater of 4096 and the passed-in max_read.
+  if (block_size < 4096) {
     fprintf(stderr, "block size (%u) is too small\n", block_size);
     return -1;
   }
@@ -382,14 +383,14 @@ int run_fuse_sideload(struct provider_vtab* vtab, void* cookie,
     return -1;
   }
 
-    struct fuse_data fd;
-    memset(&fd, 0, sizeof(fd));
+  struct fuse_data fd = {};
   fd.vtab = vtab;
   fd.cookie = cookie;
   fd.file_size = file_size;
   fd.block_size = block_size;
   fd.file_blocks = (file_size == 0) ? 0 : (((file_size - 1) / block_size) + 1);
 
+  int result;
   if (fd.file_blocks > (1 << 18)) {
     fprintf(stderr, "file has too many blocks (%u)\n", fd.file_blocks);
     result = -1;
@@ -428,18 +429,19 @@ int run_fuse_sideload(struct provider_vtab* vtab, void* cookie,
     goto done;
   }
 
-    char opts[256];
-    snprintf(opts, sizeof(opts),
-             ("fd=%d,user_id=%d,group_id=%d,max_read=%u,"
-              "allow_other,rootmode=040000"),
-             fd.ffd, fd.uid, fd.gid, block_size);
+  {
+    std::string opts = android::base::StringPrintf(
+        "fd=%d,user_id=%d,group_id=%d,max_read=%u,allow_other,rootmode=040000", fd.ffd, fd.uid,
+        fd.gid, block_size);
 
-    result = mount("/dev/fuse", FUSE_SIDELOAD_HOST_MOUNTPOINT,
-                   "fuse", MS_NOSUID | MS_NODEV | MS_RDONLY | MS_NOEXEC, opts);
+    result = mount("/dev/fuse", FUSE_SIDELOAD_HOST_MOUNTPOINT, "fuse",
+                   MS_NOSUID | MS_NODEV | MS_RDONLY | MS_NOEXEC, opts.c_str());
     if (result < 0) {
       perror("mount");
       goto done;
     }
+  }
+
   uint8_t request_buffer[sizeof(struct fuse_in_header) + PATH_MAX * 8];
   for (;;) {
     ssize_t len = TEMP_FAILURE_RETRY(read(fd.ffd, request_buffer, sizeof(request_buffer)));
@@ -452,12 +454,12 @@ int run_fuse_sideload(struct provider_vtab* vtab, void* cookie,
       continue;
     }
 
-        if ((size_t)len < sizeof(struct fuse_in_header)) {
-            fprintf(stderr, "request too short: len=%zu\n", (size_t)len);
+    if (static_cast<size_t>(len) < sizeof(struct fuse_in_header)) {
+      fprintf(stderr, "request too short: len=%zd\n", len);
       continue;
     }
 
-        struct fuse_in_header* hdr = (struct fuse_in_header*) request_buffer;
+    struct fuse_in_header* hdr = reinterpret_cast<struct fuse_in_header*>(request_buffer);
     void* data = request_buffer + sizeof(struct fuse_in_header);
 
     result = -ENOSYS;

tests/Android.mk

@@ -126,6 +126,7 @@ LOCAL_STATIC_LIBRARIES := \
     libimgpatch \
     libbsdiff \
     libbspatch \
+    libfusesideload \
     libotafault \
     librecovery \
     libupdater \

tests/component/sideload_test.cpp

@@ -13,9 +13,24 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 #include <unistd.h>
+
 #include <gtest/gtest.h>
 
-TEST(SideloadTest, fusedevice) {
-  ASSERT_NE(-1, access("/dev/fuse", R_OK | W_OK));
+#include "fuse_sideload.h"
+
+TEST(SideloadTest, fuse_device) {
+  ASSERT_EQ(0, access("/dev/fuse", R_OK | W_OK));
+}
+
+TEST(SideloadTest, run_fuse_sideload_wrong_parameters) {
+  provider_vtab vtab;
+  vtab.close = [](void*) {};
+
+  ASSERT_EQ(-1, run_fuse_sideload(&vtab, nullptr, 4096, 4095));
+  ASSERT_EQ(-1, run_fuse_sideload(&vtab, nullptr, 4096, (1 << 22) + 1));
+
+  // Too many blocks.
+  ASSERT_EQ(-1, run_fuse_sideload(&vtab, nullptr, ((1 << 18) + 1) * 4096, 4096));
 }