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Avoid using stdio streams after they have been closed. (#89)

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* 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.
This commit is contained in:
Todd C. Miller 2020-07-27 01:03:58 -06:00 committed by GitHub
parent 2a4146ec30
commit b82b649aa6
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1 changed files with 9 additions and 1 deletions
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10
run.c
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@ -1846,7 +1846,10 @@ const char *filename(FILE *fp)
continue; continue;
if (ferror(files[i].fp)) if (ferror(files[i].fp))
FATAL("i/o error occurred on %s", files[i].fname); 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; stat = pclose(files[i].fp) == -1;
else else
stat = fclose(files[i].fp) == EOF; stat = fclose(files[i].fp) == EOF;
@ -1856,6 +1859,7 @@ const char *filename(FILE *fp)
xfree(files[i].fname); xfree(files[i].fname);
files[i].fname = NULL; /* watch out for ref thru this */ files[i].fname = NULL; /* watch out for ref thru this */
files[i].fp = NULL; files[i].fp = NULL;
break;
} }
tempfree(x); tempfree(x);
x = gettemp(); x = gettemp();
@ -1873,8 +1877,12 @@ void closeall(void)
continue; continue;
if (ferror(files[i].fp)) if (ferror(files[i].fp))
FATAL( "i/o error occurred on %s", files[i].fname ); FATAL( "i/o error occurred on %s", files[i].fname );
if (files[i].fp == stdin)
continue;
if (files[i].mode == '|' || files[i].mode == LE) if (files[i].mode == '|' || files[i].mode == LE)
stat = pclose(files[i].fp) == -1; stat = pclose(files[i].fp) == -1;
else if (files[i].fp == stdout || files[i].fp == stderr)
stat = fflush(files[i].fp) == EOF;
else else
stat = fclose(files[i].fp) == EOF; stat = fclose(files[i].fp) == EOF;
if (stat) if (stat)