From: "H.J. Lu" <hjl.tools@gmail.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Binutils <binutils@sourceware.org>, Alan Modra <amodra@gmail.com>
Subject: Re: [PATCH] x86: avoid i386_dis_printf()'s staging area for potentially long strings
Date: Mon, 15 Aug 2022 07:25:14 -0700 [thread overview]
Message-ID: <CAMe9rOoKER+Q7OKqx=h_SaN8_VW7129NRT2MD79Ekh8G7coWaw@mail.gmail.com> (raw)
In-Reply-To: <cd104bce-4056-0293-a776-9fd3a6803579@suse.com>
On Mon, Aug 15, 2022 at 4:17 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> PR binutils/29483
>
> When print_insn() processes op_txt[], it may pass strings into
> i386_dis_printf() which staging_area[] cannot fit; this was observed for
> an invalid form of VPSCATTERDD (both broadcast and zeroing-masking bits
> set). Rather than arbitrarily enlarging that local array, avoid its use
> altogether when the format string is simply "%s". This merely requires
> two local variables to have their type constified.
>
> While limiting the scope of "res" it became apparent that
> - no caller cares about the function's return value,
> - the comment about the return value was wrong,
> - a particular positive return value would have been meaningless to the
> caller.
> Therefore convert the function to return "void" at the same time.
> ---
> An alternative to the special casing would be to introduce something
> like i386_dis_puts(), then to be used by all call sites which currently
> pass "%s" or format strings without any format characters at all (plus,
> of course, i386_dis_printf() itself).
>
> --- a/opcodes/i386-dis.c
> +++ b/opcodes/i386-dis.c
> @@ -9264,31 +9264,40 @@ oappend_register (instr_info *ins, const
> STYLE is the default style to use in the fprintf_styled_func calls,
> however, FMT might include embedded style markers (see oappend_style),
> these embedded markers are not printed, but instead change the style
> - used in the next fprintf_styled_func call.
> + used in the next fprintf_styled_func call. */
>
> - Return non-zero to indicate the print call was a success. */
> -
> -static int ATTRIBUTE_PRINTF_3
> +static void ATTRIBUTE_PRINTF_3
> i386_dis_printf (instr_info *ins, enum disassembler_style style,
> const char *fmt, ...)
> {
> va_list ap;
> enum disassembler_style curr_style = style;
> - char *start, *curr;
> + const char *start, *curr;
> char staging_area[100];
> - int res;
>
> va_start (ap, fmt);
> - res = vsnprintf (staging_area, sizeof (staging_area), fmt, ap);
> - va_end (ap);
> + /* In particular print_insn()'s processing of op_txt[] can hand rather long
> + strings here. Bypass vsnprintf() in such cases to avoid capacity issues
> + with the staging area. */
> + if (strcmp (fmt, "%s"))
> + {
> + int res = vsnprintf (staging_area, sizeof (staging_area), fmt, ap);
>
> - if (res < 0)
> - return res;
> + va_end (ap);
>
> - if ((size_t) res >= sizeof (staging_area))
> - abort ();
> + if (res < 0)
> + return;
>
> - start = curr = staging_area;
> + if ((size_t) res >= sizeof (staging_area))
> + abort ();
> +
> + start = curr = staging_area;
> + }
> + else
> + {
> + start = curr = va_arg (ap, const char *);
> + va_end (ap);
> + }
>
> do
> {
> @@ -9303,10 +9312,7 @@ i386_dis_printf (instr_info *ins, enum d
> curr_style,
> "%.*s", len, start);
> if (n < 0)
> - {
> - res = n;
> - break;
> - }
> + break;
>
> if (*curr == '\0')
> break;
> @@ -9340,8 +9346,6 @@ i386_dis_printf (instr_info *ins, enum d
> ++curr;
> }
> while (true);
> -
> - return res;
> }
>
> static int
Please include a testcase to verify that the issue is fixed.
Thanks.
--
H.J.
next prev parent reply other threads:[~2022-08-15 14:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-15 11:17 Jan Beulich
2022-08-15 14:25 ` H.J. Lu [this message]
2022-08-15 14:39 ` Jan Beulich
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