From nobody Fri Apr 3 02:56:38 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6548730EF8F for ; Wed, 25 Mar 2026 13:27:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774445276; cv=none; b=OU4XA8v5/mQkCYHW5DWKHPsn6BGpbgkkT0gWhrpwC3/C474roXqLGNCI8r3lebIZN5FNlMeoTNKh5IrV488bdhYPftH4DbSOSdwNr2Kvk/UVTbQ0ORq/zBcnSjQva4914FWa+csED6GxW/cFiyTxcADmwxeVI73kOus5sEML5W0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774445276; c=relaxed/simple; bh=BBxzzkxMTmP+iLsf1M+FE7ie2lV9X0l6E4sxyncTgf0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=qTuhuPRFSIETMmPLY4aB80BJTMefxEZY+Sl89bCmzDj74w2EVurInC+lc97njV1JfqCeAiUoo1opQ0yqlKrO0+QrrdmqVpdxYFl1VToP7NNXTGbuGByC6QpL78BYTrTWSAd3RpbuF1ZI9KTGjmf2NjJF8YczmJv+nPXc3dIoQss= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KlwqkByM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KlwqkByM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EDC3EC4CEF7; Wed, 25 Mar 2026 13:27:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774445276; bh=BBxzzkxMTmP+iLsf1M+FE7ie2lV9X0l6E4sxyncTgf0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KlwqkByMJZXoPMpqDiWc0bSbz8vrxQxVGpl7auAv8BphZ43QWWDGtkhHaOl8R11Uo A91SxGijTtyLeRTrpvhIiIjbFyK3pVOZHxXZxj9zh9+51uoH6v3633rvBTdQh4KqqK s25ThNXrlWMMWwizD7FJvAKPGviLErQLes8684Uqs7pAv9BKWlDLPzyjJpKaVM8g+Y swTGmaFtiCP5G9oip7BMx5cUOXRDlkahASFxY+fO+ErWDJmRdmHoqb2Xw6NXHx9345 fAiPSLBAj4Dh9X+Lrmars7Flx9OaBy1zaCQoI86AFDJzLFidRyWt+ZmymMASf+SGkL KBnGljk39u28A== From: "Masami Hiramatsu (Google)" To: Petr Mladek , Steven Rostedt , Andy Shevchenko Cc: Rasmus Villemoes , Sergey Senozhatsky , Andrew Morton , David Laight , linux-kernel@vger.kernel.org Subject: [PATCH v5 2/2] lib/vsprintf: Limit the returning size to INT_MAX Date: Wed, 25 Mar 2026 22:27:51 +0900 Message-ID: <177444527112.185641.7354813978127876075.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <177444525139.185641.12184379647176430297.stgit@devnote2> References: <177444525139.185641.12184379647176430297.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: Masami Hiramatsu (Google) The return value of vsnprintf() and bstr_printf() can overflow INT_MAX and return a minus value. In the @size is checked input overflow, but it does not check the output, which is expected required size. This should never happen but it should be checked and limited. Signed-off-by: Masami Hiramatsu (Google) --- Changes in v5: - Fix bstr_printf() too. Changes in v4: - Add Petr's reviewed-by. (Thanks!) Changes in v3: - Use local variable for better readability. --- lib/vsprintf.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 2f6b7179f581..69dec9b18428 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2859,6 +2859,7 @@ static unsigned long long convert_num_spec(unsigned i= nt val, int size, struct pr int vsnprintf(char *buf, size_t size, const char *fmt_str, va_list args) { char *str, *end; + size_t ret_size; struct printf_spec spec =3D {0}; struct fmt fmt =3D { .str =3D fmt_str, @@ -2978,8 +2979,12 @@ int vsnprintf(char *buf, size_t size, const char *fm= t_str, va_list args) } =20 /* the trailing null byte doesn't count towards the total */ - return str-buf; + ret_size =3D str - buf; =20 + /* Make sure the return value is within the positive integer range */ + if (WARN_ON_ONCE(ret_size > INT_MAX)) + ret_size =3D INT_MAX; + return ret_size; } EXPORT_SYMBOL(vsnprintf); =20 @@ -3283,6 +3288,7 @@ int bstr_printf(char *buf, size_t size, const char *f= mt_str, const u32 *bin_buf) struct printf_spec spec =3D {0}; char *str, *end; const char *args =3D (const char *)bin_buf; + size_t ret_size; =20 if (WARN_ON_ONCE(size > INT_MAX)) return 0; @@ -3431,7 +3437,12 @@ int bstr_printf(char *buf, size_t size, const char *= fmt_str, const u32 *bin_buf) #undef get_arg =20 /* the trailing null byte doesn't count towards the total */ - return str - buf; + ret_size =3D str - buf; + + /* Make sure the return value is within the positive integer range */ + if (WARN_ON_ONCE(ret_size > INT_MAX)) + ret_size =3D INT_MAX; + return ret_size; } EXPORT_SYMBOL_GPL(bstr_printf);