Correct some code in pg_restore when reading the header of a tar archive:

(1) The code doesn't initialize `sum', so the initial "does the checksum
    match?" test is wrong.

(2) The loop that is intended to check for a "null block" just checks
    the first byte of the tar block 512 times, rather than each of the
    512 bytes one time (!), which I'm guessing was the intent.

It was only through sheer luck that this worked in the first place.

Per Coverity static analysis performed by EnterpriseDB.

diff --git a/src/bin/pg_dump/pg_backup_tar.c b/src/bin/pg_dump/pg_backup_tar.c
index 1465585f90896468ce3d266207889e47c9ae14a5..a66eada206270ff5f45addfbddf0c2d44cf6e3e0 100644 (file)
--- a/src/bin/pg_dump/pg_backup_tar.c
+++ b/src/bin/pg_dump/pg_backup_tar.c
@@ -1153,7 +1153,6 @@ _tarGetHeader(ArchiveHandle *AH, TAR_MEMBER *th)
        size_t          len;
        unsigned long ullen;
        off_t           hPos;
-       int                     i;
        bool            gotBlock = false;
 
        while (!gotBlock)
@@ -1176,7 +1175,7 @@ _tarGetHeader(ArchiveHandle *AH, TAR_MEMBER *th)
                hPos = ctx->tarFHpos;
 
                /* Read a 512 byte block, return EOF, exit if short */
-               len = _tarReadRaw(AH, &h[0], 512, NULL, ctx->tarFH);
+               len = _tarReadRaw(AH, h, 512, NULL, ctx->tarFH);
                if (len == 0)                   /* EOF */
                        return 0;
 
@@ -1186,20 +1185,22 @@ _tarGetHeader(ArchiveHandle *AH, TAR_MEMBER *th)
                                                 (unsigned long) len);
 
                /* Calc checksum */
-               chk = _tarChecksum(&h[0]);
+               chk = _tarChecksum(h);
+               sscanf(&h[148], "%8o", &sum);
 
                /*
-                * If the checksum failed, see if it is a null block. If so, then
-                * just try with next block...
+                * If the checksum failed, see if it is a null block. If so,
+                * silently continue to the next block.
                 */
-
                if (chk == sum)
                        gotBlock = true;
                else
                {
+                       int                     i;
+
                        for (i = 0; i < 512; i++)
                        {
-                               if (h[0] != 0)
+                               if (h[i] != 0)
                                {
                                        gotBlock = true;
                                        break;
@@ -1211,7 +1212,6 @@ _tarGetHeader(ArchiveHandle *AH, TAR_MEMBER *th)
        sscanf(&h[0], "%99s", tag);
        sscanf(&h[124], "%12lo", &ullen);
        len = (size_t) ullen;
-       sscanf(&h[148], "%8o", &sum);
 
        {
                char            buf[100];