Check an edge case when read(2) returns 0

We might end up in an infinite loop if read(2) reached EOF unexpectedly.
The problematic code in uncrypt mentioned in the bug has been fixed
by switching to libbase ReadFully(). So I grepped through the recovery
code and fixed some other occurences of the issue.

Bug: 31073201
Change-Id: Ib867029158ba23363b8f85d61c25058a635c5a6b

3 files changed, 12 insertions, 8 deletions

diff --git a/applypatch/applypatch.cpp b/applypatch/applypatch.cpp
index 02a3c6e4..e52ef99d 100644
--- a/applypatch/applypatch.cpp
+++ b/applypatch/applypatch.cpp
@@ -336,6 +336,9 @@ int WriteToPartition(const unsigned char* data, size_t len, const char* target)
                     printf("verify read error %s at %zu: %s\n",
                            partition, p, strerror(errno));
                     return -1;
+                } else if (read_count == 0) {
+                    printf("verify read reached unexpected EOF, %s at %zu\n", partition, p);
+                    return -1;
                 }
                 if (static_cast<size_t>(read_count) < to_read) {
                     printf("short verify read %s at %zu: %zd %zu %s\n",
diff --git a/fuse_sdcard_provider.cpp b/fuse_sdcard_provider.cpp
index df963127..b0ecf96b 100644
--- a/fuse_sdcard_provider.cpp
+++ b/fuse_sdcard_provider.cpp
@@ -23,6 +23,8 @@
 #include <unistd.h>
 #include <fcntl.h>
 
+#include <android-base/file.h>
+
 #include "fuse_sideload.h"
 
 struct file_data {
@@ -41,14 +43,9 @@ static int read_block_file(void* cookie, uint32_t block, uint8_t* buffer, uint32
         return -EIO;
     }
 
-    while (fetch_size > 0) {
-        ssize_t r = TEMP_FAILURE_RETRY(read(fd->fd, buffer, fetch_size));
-        if (r == -1) {
-            fprintf(stderr, "read on sdcard failed: %s\n", strerror(errno));
-            return -EIO;
-        }
-        fetch_size -= r;
-        buffer += r;
+    if (!android::base::ReadFully(fd->fd, buffer, fetch_size)) {
+        fprintf(stderr, "read on sdcard failed: %s\n", strerror(errno));
+        return -EIO;
     }
 
     return 0;
diff --git a/updater/blockimg.cpp b/updater/blockimg.cpp
index f00bc4bf..0caa1acb 100644
--- a/updater/blockimg.cpp
+++ b/updater/blockimg.cpp
@@ -151,6 +151,10 @@ static int read_all(int fd, uint8_t* data, size_t size) {
             failure_type = kFreadFailure;
             fprintf(stderr, "read failed: %s\n", strerror(errno));
             return -1;
+        } else if (r == 0) {
+            failure_type = kFreadFailure;
+            fprintf(stderr, "read reached unexpected EOF.\n");
+            return -1;
         }
         so_far += r;
     }