svn commit: r257320 - stable/10/lib/libc/gen

[Gleb Smirnoff]

Author: glebius
Date: Tue Oct 29 09:23:51 2013
New Revision: 257320
URL: http://svnweb.freebsd.org/changeset/base/257320

Log:
  Merge r256537 from head:
      Make getutxent(3) more robust against bad utx.log files. Whenever we read
    zeroes, don't stop processing the file, but read until its end or valid
    data.
  
    In collaboration with:	ed
  
  Approved by:	re (kib)

Modified:
  stable/10/lib/libc/gen/getutxent.c
Directory Properties:
  stable/10/lib/libc/   (props changed)

Modified: stable/10/lib/libc/gen/getutxent.c
==============================================================================
--- stable/10/lib/libc/gen/getutxent.c	Tue Oct 29 09:04:25 2013	(r257319)
+++ stable/10/lib/libc/gen/getutxent.c	Tue Oct 29 09:23:51 2013	(r257320)
@@ -122,9 +122,20 @@ getfutxent(struct futx *fu)
 	if (udb == UTXDB_LOG) {
 		uint16_t len;
 
+retry:
 		if (fread(&len, sizeof(len), 1, uf) != 1)
 			return (-1);
 		len = be16toh(len);
+		if (len == 0) {
+			/*
+			 * XXX: Though zero-size records are valid in theory,
+			 * they can never occur in practice. Zero-size records
+			 * indicate file corruption. Seek one byte forward, to
+			 * see if we can find a record there.
+			 */
+			ungetc('\0', uf);
+			goto retry;
+		}
 		if (len > sizeof *fu) {
 			/* Forward compatibility. */
 			if (fread(fu, sizeof(*fu), 1, uf) != 1)