From b82b649aa65fbdff45869d1fd6d72fd2b85946cd Mon Sep 17 00:00:00 2001 From: "Todd C. Miller" Date: Mon, 27 Jul 2020 01:03:58 -0600 Subject: [PATCH] Avoid using stdio streams after they have been closed. (#89) * In closeall(), skip stdin and flush std{err,out} instead of closing. Otherwise awk could fclose(stdin) twice (it may appear more than once) and closing stderr means awk cannot report errors with other streams. For example, "awk 'BEGIN { getline < "-" }' < /dev/null" will call fclose(stdin) twice, with undefined results. * If closefile() is called on std{in,out,err}, freopen() /dev/null instead. Otherwise, awk will continue trying to perform I/O on a closed stdio stream, the behavior of which is undefined. --- run.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/run.c b/run.c index 98787f1..bb6b7fe 100644 --- a/run.c +++ b/run.c @@ -1846,7 +1846,10 @@ const char *filename(FILE *fp) continue; if (ferror(files[i].fp)) FATAL("i/o error occurred on %s", files[i].fname); - if (files[i].mode == '|' || files[i].mode == LE) + if (files[i].fp == stdin || files[i].fp == stdout || + files[i].fp == stderr) + stat = freopen("/dev/null", "r+", files[i].fp) == NULL; + else if (files[i].mode == '|' || files[i].mode == LE) stat = pclose(files[i].fp) == -1; else stat = fclose(files[i].fp) == EOF; @@ -1856,6 +1859,7 @@ const char *filename(FILE *fp) xfree(files[i].fname); files[i].fname = NULL; /* watch out for ref thru this */ files[i].fp = NULL; + break; } tempfree(x); x = gettemp(); @@ -1873,8 +1877,12 @@ void closeall(void) continue; if (ferror(files[i].fp)) FATAL( "i/o error occurred on %s", files[i].fname ); + if (files[i].fp == stdin) + continue; if (files[i].mode == '|' || files[i].mode == LE) stat = pclose(files[i].fp) == -1; + else if (files[i].fp == stdout || files[i].fp == stderr) + stat = fflush(files[i].fp) == EOF; else stat = fclose(files[i].fp) == EOF; if (stat)