machined: add early checks for unrealistically large image/pool sizes

src/basic/btrfs-util.c

@@ -43,6 +43,7 @@
 #include "copy.h"
 #include "fd-util.h"
 #include "fileio.h"
+#include "io-util.h"
 #include "macro.h"
 #include "missing.h"
 #include "path-util.h"
@@ -913,6 +914,10 @@ int btrfs_resize_loopback_fd(int fd, uint64_t new_size, bool grow_only) {
         dev_t dev = 0;
         int r;
 
+        /* In contrast to btrfs quota ioctls ftruncate() cannot make sense of "infinity" or file sizes > 2^31 */
+        if (!FILE_SIZE_VALID(new_size))
+                return -EINVAL;
+
         /* btrfs cannot handle file systems < 16M, hence use this as minimum */
         if (new_size < 16*1024*1024)
                 new_size = 16*1024*1024;

src/basic/io-util.h

@@ -77,3 +77,21 @@ static inline size_t IOVEC_INCREMENT(struct iovec *i, unsigned n, size_t k) {
 
         return k;
 }
+
+static inline bool FILE_SIZE_VALID(uint64_t l) {
+        /* ftruncate() and friends take an unsigned file size, but actually cannot deal with file sizes larger than
+         * 2^63 since the kernel internally handles it as signed value. This call allows checking for this early. */
+
+        return (l >> 63) == 0;
+}
+
+static inline bool FILE_SIZE_VALID_OR_INFINITY(uint64_t l) {
+
+        /* Same as above, but allows one extra value: -1 as indication for infinity. */
+
+        if (l == (uint64_t) -1)
+                return true;
+
+        return FILE_SIZE_VALID(l);
+
+}