On 12/29/18 5:05 PM, leo_...@volny.cz wrote:
> zeur here.
>
> The following {,ab}use of tail(1):
>
> % </var/log/messages tail -f
>
> causes an abort trap 'cause of a missing "rpath" pledge. An excellent
> demonstration of pledge(2)'s usefulness, since it exposed a little bug
> that caused tail to try and re-open stdin, which is useless on
> OpenBSD[0] (unless we parse stdin as "/dev/stdin" and its ino would
> change -- unlikely).
>
> The below patch fixes this by simply not trying to re-open stdin.
>
> --zeurkous.
>
> [0] NetBSD, iirc, keeps track of the original path of opened files
> (other systems might too), but I suppose that's irrelevant here :)
>
I'd like to propose a slightly different diff, since POSIX states that a
filename "-" should mean stdin I would like to prepare the struct
tailfile to contain the is_stdin element, so this can be added a little
easier in the future.
OK?
martijn@
Index: extern.h
===================================================================
RCS file: /cvs/src/usr.bin/tail/extern.h,v
retrieving revision 1.12
diff -u -p -r1.12 extern.h
--- extern.h 19 Nov 2015 17:50:04 -0000 1.12
+++ extern.h 2 Jan 2019 08:52:28 -0000
@@ -40,6 +40,7 @@ struct tailfile {
char *fname;
FILE *fp;
struct stat sb;
+ int is_stdin;
};
enum STYLE { NOTSET = 0, FBYTES, FLINES, RBYTES, RLINES, REVERSE };
Index: forward.c
===================================================================
RCS file: /cvs/src/usr.bin/tail/forward.c,v
retrieving revision 1.31
diff -u -p -r1.31 forward.c
--- forward.c 5 Jul 2016 05:06:27 -0000 1.31
+++ forward.c 2 Jan 2019 08:52:28 -0000
@@ -335,7 +335,8 @@ tfreopen(struct tailfile *tf) {
struct tailfile **treopen, *ttf;
int i;
- if (tf && ((stat(tf->fname, &sb) != 0) || sb.st_ino != tf->sb.st_ino)) {
+ if (tf && !tf->is_stdin &&
+ ((stat(tf->fname, &sb) != 0) || sb.st_ino != tf->sb.st_ino)) {
if (afiles < ++nfiles) {
afiles += AFILESINCR;
treopen = reallocarray(reopen, afiles, sizeof(*reopen));
Index: tail.c
===================================================================
RCS file: /cvs/src/usr.bin/tail/tail.c,v
retrieving revision 1.21
diff -u -p -r1.21 tail.c
--- tail.c 3 Feb 2016 12:23:57 -0000 1.21
+++ tail.c 2 Jan 2019 08:52:28 -0000
@@ -45,7 +45,6 @@
#include "extern.h"
int fflag, rflag, rval;
-int is_stdin;
static void obsolete(char **);
static void usage(void);
@@ -155,6 +154,7 @@ main(int argc, char *argv[])
if (argc) {
for (i = 0; *argv; i++) {
tf[i].fname = *argv++;
+ tf[i].is_stdin = 0;
if ((tf[i].fp = fopen(tf[i].fname, "r")) == NULL ||
fstat(fileno(tf[i].fp), &(tf[i].sb))) {
ierr(tf[i].fname);
@@ -173,7 +173,7 @@ main(int argc, char *argv[])
tf[0].fname = "stdin";
tf[0].fp = stdin;
- is_stdin = 1;
+ tf[0].is_stdin = 1;
if (fstat(fileno(stdin), &(tf[0].sb))) {
ierr(tf[0].fname);
