Author: jilles
Date: Sat Jun 20 20:44:27 2009
New Revision: 194560
URL: http://svn.freebsd.org/changeset/base/194560
Log:
Fix race condition in noclobber option.
Formerly, it was possible for the file to be created between the check if it
existed and the open; the contents would then be lost.
Because this must use O_EXCL, noclobber > will not create a file through a
symlink anymore. This agrees with behaviour of other shells.
Approved by: ed (mentor) (implicit)
Modified:
head/bin/sh/redir.c
Modified: head/bin/sh/redir.c
==============================================================================
--- head/bin/sh/redir.c Sat Jun 20 20:36:51 2009 (r194559)
+++ head/bin/sh/redir.c Sat Jun 20 20:44:27 2009 (r194560)
@@ -188,13 +188,25 @@ movefd:
error("cannot create %s: %s", fname, strerror(errno));
goto movefd;
case NTO:
- fname = redir->nfile.expfname;
- if (Cflag && stat(fname, &sb) != -1 && S_ISREG(sb.st_mode))
- error("cannot create %s: %s", fname,
- strerror(EEXIST));
- if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
- error("cannot create %s: %s", fname, strerror(errno));
- goto movefd;
+ if (Cflag) {
+ fname = redir->nfile.expfname;
+ if (stat(fname, &sb) == -1) {
+ if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL,
0666)) < 0)
+ error("cannot create %s: %s", fname,
strerror(errno));
+ } else if (!S_ISREG(sb.st_mode)) {
+ if ((f = open(fname, O_WRONLY, 0666)) < 0)
+ error("cannot create %s: %s", fname,
strerror(errno));
+ if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode))
{
+ close(f);
+ error("cannot create %s: %s", fname,
+ strerror(EEXIST));
+ }
+ } else
+ error("cannot create %s: %s", fname,
+ strerror(EEXIST));
+ goto movefd;
+ }
+ /* FALLTHROUGH */
case NCLOBBER:
fname = redir->nfile.expfname;
if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
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