tar: cry murder and bail out if file shrinks under us while we tar it up

git-svn-id: svn://busybox.net/trunk/busybox@16653 69ca8d6d-28ef-0310-b511-8ec308f3f277

1 files changed, 12 insertions, 2 deletions

diff --git a/archival/tar.c b/archival/tar.c
index 6aaa42273..99c4adb6a 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -59,7 +59,7 @@ struct TarHeader {		  /* byte offset */
 typedef struct TarHeader TarHeader;
 
 /*
-** writeTarFile(),  writeFileToTarball(), and writeTarHeader() are
+** writeTarFile(), writeFileToTarball(), and writeTarHeader() are
 ** the only functions that deal with the HardLinkInfo structure.
 ** Even these functions use the xxxHardLinkInfo() functions.
 */
@@ -397,7 +397,17 @@ static int writeFileToTarball(const char *fileName, struct stat *statbuf,
                 off_t readSize = 0;
 
                 /* write the file to the archive */
-                readSize = bb_copyfd_eof(inputFileFd, tbInfo->tarFd);
+                readSize = bb_copyfd_size(inputFileFd, tbInfo->tarFd, statbuf->st_size);
+                if (readSize != statbuf->st_size) {
+                        /* Deadly. We record size into header first, */
+                        /* and then write out file. If file shrinks in between, */
+                        /* tar will be corrupted. So bail out. */
+                        /* NB: GNU tar 1.16 warns and pads with zeroes */
+                        /* or even seeks back and updates header */
+                        bb_error_msg_and_die("short read from %s", fileName);
+                }
+                /* Check that file did not grow in between? */
+                /* if (safe_read(inputFileFd,1) == 1) warn but continue? */
                 close(inputFileFd);
 
                 /* Pad the file up to the tar block size */