Author: ed
Date: Sat Feb 11 11:11:13 2012
New Revision: 231514
URL: http://svn.freebsd.org/changeset/base/231514
Log:
Set read buffer size to multiple of sizeof(struct futx).
If the utmpx database gets updated while an application is reading it,
there is a chance the reading application processes partially
overwritten entries. To solve this, make sure we always read a multiple
of sizeof(struct futx) at a time.
MFC after: 2 weeks
Modified:
head/lib/libc/gen/getutxent.c
Modified: head/lib/libc/gen/getutxent.c
==============================================================================
--- head/lib/libc/gen/getutxent.c Sat Feb 11 08:58:12 2012
(r231513)
+++ head/lib/libc/gen/getutxent.c Sat Feb 11 11:11:13 2012
(r231514)
@@ -70,13 +70,18 @@ setutxdb(int db, const char *file)
if (uf == NULL)
return (-1);
- /* Safety check: never use broken files. */
- if (db != UTXDB_LOG && _fstat(fileno(uf), &sb) != -1 &&
- sb.st_size % sizeof(struct futx) != 0) {
- fclose(uf);
- uf = NULL;
- errno = EFTYPE;
- return (-1);
+ if (db != UTXDB_LOG) {
+ /* Safety check: never use broken files. */
+ if (_fstat(fileno(uf), &sb) != -1 &&
+ sb.st_size % sizeof(struct futx) != 0) {
+ fclose(uf);
+ uf = NULL;
+ errno = EFTYPE;
+ return (-1);
+ }
+ /* Prevent reading of partial records. */
+ (void)setvbuf(uf, NULL, _IOFBF,
+ rounddown(BUFSIZ, sizeof(struct futx)));
}
udb = db;
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