[PATCH 09/20] tempfile: handle NULL tempfile pointers gracefully
From: Jeff King <hidden>
Date: 2017-09-05 12:15:03
Subsystem:
the rest · Maintainer:
Linus Torvalds
The tempfile functions all take pointers to tempfile
objects, but do not check whether the argument is NULL.
This isn't a big deal in practice, since the lifetime of any
tempfile object is defined to last for the whole program. So
even if we try to call delete_tempfile() on an
already-deleted tempfile, our "active" check will tell us
that it's a noop.
In preparation for transitioning to a new system that
loosens the "tempfile objects can never be freed" rule,
let's tighten up our active checks:
1. A NULL pointer is now defined as "inactive" (so it will
BUG for most functions, but works as a silent noop for
things like delete_tempfile).
2. Functions should always do the "active" check before
looking at any of the struct fields.
Signed-off-by: Jeff King <redacted>
---
tempfile.c | 12 +++++++-----
tempfile.h | 2 +-
2 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/tempfile.c b/tempfile.c
index 964c66d504..861f817133 100644
--- a/tempfile.c
+++ b/tempfile.c@@ -236,13 +236,15 @@ FILE *get_tempfile_fp(struct tempfile *tempfile) int close_tempfile_gently(struct tempfile *tempfile) { - int fd = tempfile->fd; - FILE *fp = tempfile->fp; + int fd; + FILE *fp; int err; - if (fd < 0) + if (!is_tempfile_active(tempfile) || tempfile->fd < 0) return 0; + fd = tempfile->fd; + fp = tempfile->fp; tempfile->fd = -1; if (fp) { tempfile->fp = NULL;
@@ -262,10 +264,10 @@ int close_tempfile_gently(struct tempfile *tempfile) int reopen_tempfile(struct tempfile *tempfile) { - if (0 <= tempfile->fd) - die("BUG: reopen_tempfile called for an open object"); if (!is_tempfile_active(tempfile)) die("BUG: reopen_tempfile called for an inactive object"); + if (0 <= tempfile->fd) + die("BUG: reopen_tempfile called for an open object"); tempfile->fd = open(tempfile->filename.buf, O_WRONLY); return tempfile->fd; }
diff --git a/tempfile.h b/tempfile.h
index d854dcdd3e..d30663182d 100644
--- a/tempfile.h
+++ b/tempfile.h@@ -211,7 +211,7 @@ extern FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode); static inline int is_tempfile_active(struct tempfile *tempfile) { - return tempfile->active; + return tempfile && tempfile->active; } /*
--
2.14.1.721.gc5bc1565f1