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From: Denys Vlasenko <vda.linux@googlemail.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: DASH shell mailing list <dash@vger.kernel.org>
Subject: Re: [PATCH] parser: Fix VSLENGTH parsing with trailing garbage
Date: Mon, 21 Jun 2021 16:21:40 +0200	[thread overview]
Message-ID: <CAK1hOcNdGJNyCLiRwnw1N0wj6F+CZnFL9VNVQ2v0=YeGwCpQsw@mail.gmail.com> (raw)
In-Reply-To: <20210621095719.GA9287@gondor.apana.org.au>

On Mon, Jun 21, 2021 at 11:57 AM Herbert Xu <herbert@gondor.apana.org.au> wrote:
> On Sat, Jun 19, 2021 at 02:44:46PM +0200, Denys Vlasenko wrote:
> > CTLVAR and CTLBACKQ are not properly handled if encountered
> > inside {$#...}. Testcase:
> >
> > dash -c "`printf 'echo ${#1\x82}'`" 00 111 222
...
> In fact these two bugs are one and the same.  This patch fixes
> both by detecting the invalid substitution and not emitting it
> into the node tree.
>
> Incidentally this reveals a bug in how we parse ${#10} that got
> introduced recently, which is also fixed here.
...
> --- a/src/parser.h
> +++ b/src/parser.h
> @@ -62,6 +62,7 @@
>  #define VSTRIMLEFT     0x8             /* ${var#pattern} */
>  #define VSTRIMLEFTMAX  0x9             /* ${var##pattern} */
>  #define VSLENGTH       0xa             /* ${#var} */
> +/* VSLENGTH must come last. */

The above assumption is not necessary if...


> diff --git a/src/parser.c b/src/parser.c
> index 3c80d17..13c2df5 100644
> --- a/src/parser.c
> +++ b/src/parser.c
> @@ -1252,7 +1252,8 @@ varname:
>                         do {
>                                 STPUTC(c, out);
>                                 c = pgetc_eatbnl();
> -                       } while (!subtype && is_digit(c));
> +                       } while ((subtype <= 0 || subtype >= VSLENGTH) &&
> +                                is_digit(c));

... you use (subtype == 0 || subtype == VSLENGTH) here.
Also, (subtype == 0 || subtype == VSLENGTH) is less confusing:
it says "loop if ${VAR} or ${#VAR} syntax", whereas <= >=
are a bit misleading.

  reply	other threads:[~2021-06-21 14:21 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-19 12:44 SEGV parsing of ${#1\x82} and ${#1\x84} Denys Vlasenko
2021-06-21  9:57 ` [PATCH] parser: Fix VSLENGTH parsing with trailing garbage Herbert Xu
2021-06-21 14:21   ` Denys Vlasenko [this message]
2021-06-22  0:19     ` Herbert Xu
2021-06-22  8:34       ` Denys Vlasenko

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