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Re: [PATCH] wordexp: Rewrite parse_tilde to use struct scratch_buffer [BZ #18023]
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Tue, 26 Jun 2018 13:59:32 -0300
- Subject: Re: [PATCH] wordexp: Rewrite parse_tilde to use struct scratch_buffer [BZ #18023]
- References: <20180626154638.723FE43994575@oldenburg.str.redhat.com>
On 26/06/2018 12:46, Florian Weimer wrote:
> 2018-06-26 Florian Weimer <fweimer@redhat.com>
>
> [BZ #18023]
> * posix/wordexp.c (parse_tilde): Use struct scratch_buffer
> instead of extend_alloca.
LGTM, thanks.
>
> diff --git a/posix/wordexp.c b/posix/wordexp.c
> index 0b669a8f5e..7548e0329f 100644
> --- a/posix/wordexp.c
> +++ b/posix/wordexp.c
> @@ -17,7 +17,6 @@
> License along with the GNU C Library; if not, see
> <http://www.gnu.org/licenses/>. */
>
> -#include <alloca.h>
> #include <ctype.h>
> #include <errno.h>
> #include <fcntl.h>
> @@ -41,6 +40,7 @@
> #include <wchar.h>
> #include <wordexp.h>
> #include <kernel-features.h>
> +#include <scratch_buffer.h>
>
> #include <libc-lock.h>
> #include <_itoa.h>
> @@ -299,12 +299,7 @@ parse_tilde (char **word, size_t *word_length, size_t *max_length,
> if (i == 1 + *offset)
> {
> /* Tilde appears on its own */
> - uid_t uid;
> - struct passwd pwd, *tpwd;
> - int buflen = 1000;
> char* home;
> - char* buffer;
> - int result;
>
> /* POSIX.2 says ~ expands to $HOME and if HOME is unset the
> results are unspecified. We do a lookup on the uid if
> @@ -319,25 +314,38 @@ parse_tilde (char **word, size_t *word_length, size_t *max_length,
> }
> else
> {
> - uid = __getuid ();
> - buffer = __alloca (buflen);
> + struct passwd pwd, *tpwd;
> + uid_t uid = __getuid ();
> + int result;
> + struct scratch_buffer tmpbuf;
> + scratch_buffer_init (&tmpbuf);
>
> - while ((result = __getpwuid_r (uid, &pwd, buffer, buflen, &tpwd)) != 0
> + while ((result = __getpwuid_r (uid, &pwd,
> + tmpbuf.data, tmpbuf.length,
> + &tpwd)) != 0
> && errno == ERANGE)
> - buffer = extend_alloca (buffer, buflen, buflen + 1000);
> + if (!scratch_buffer_grow (&tmpbuf))
> + return WRDE_NOSPACE;
>
> if (result == 0 && tpwd != NULL && pwd.pw_dir != NULL)
> {
> *word = w_addstr (*word, word_length, max_length, pwd.pw_dir);
> if (*word == NULL)
> - return WRDE_NOSPACE;
> + {
> + scratch_buffer_free (&tmpbuf);
> + return WRDE_NOSPACE;
> + }
> }
> else
> {
> *word = w_addchar (*word, word_length, max_length, '~');
> if (*word == NULL)
> - return WRDE_NOSPACE;
> + {
> + scratch_buffer_free (&tmpbuf);
> + return WRDE_NOSPACE;
> + }
> }
> + scratch_buffer_free (&tmpbuf);
> }
> }
> else
> @@ -345,13 +353,15 @@ parse_tilde (char **word, size_t *word_length, size_t *max_length,
> /* Look up user name in database to get home directory */
> char *user = strndupa (&words[1 + *offset], i - (1 + *offset));
> struct passwd pwd, *tpwd;
> - int buflen = 1000;
> - char* buffer = __alloca (buflen);
> int result;
> + struct scratch_buffer tmpbuf;
> + scratch_buffer_init (&tmpbuf);
>
> - while ((result = __getpwnam_r (user, &pwd, buffer, buflen, &tpwd)) != 0
> + while ((result = __getpwnam_r (user, &pwd, tmpbuf.data, tmpbuf.length,
> + &tpwd)) != 0
> && errno == ERANGE)
> - buffer = extend_alloca (buffer, buflen, buflen + 1000);
> + if (!scratch_buffer_grow (&tmpbuf))
> + return WRDE_NOSPACE;
>
> if (result == 0 && tpwd != NULL && pwd.pw_dir)
> *word = w_addstr (*word, word_length, max_length, pwd.pw_dir);
> @@ -363,6 +373,8 @@ parse_tilde (char **word, size_t *word_length, size_t *max_length,
> *word = w_addstr (*word, word_length, max_length, user);
> }
>
> + scratch_buffer_free (&tmpbuf);
> +
> *offset = i - 1;
> }
> return *word ? 0 : WRDE_NOSPACE;
>