From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6ABEA33993; Sat, 12 Sep 2026 17:08:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789232911; cv=none; b=JUT/Vpa7rIS8BlqxAy0oS0bMUABdmgwjSTGjIrdx8TsrzR4r/x123KWWwyAiFVV4LUXprZcsrII6iszRAuThPxZyWRpMcQv5CQYza1OnPPb6lBEPtEpdb979BkWrx0BCfiwALpFsmepwSXo/4HKYpm0Vpej31sPzK5z64WlR2GU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789232911; c=relaxed/simple; bh=1rHZ+xjHLrxnbjW8REaFojk0RYCjt6p71Hr6zBJIbos=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tkjX+bsnJ3/U7Us9wgQpX7vhmIwtsIQz23YBVghBYgI7hGFeFdCgth4J/RkvvzXXmWtnwxgNXHKtuIE2n7GqB+K3BqCAGy2MgZnHNRj/peQsXnXwhII9qRPjJB2DPz00lXIc+CRLZ9Jkd4avEamYf+D2kbVQSe9GGLVevWnIvLA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vwewnkOB; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vwewnkOB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75D141F000FF; Sat, 12 Sep 2026 17:08:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789232910; bh=MVT7qhtu2RHQ2LJGAzrnEwQzvM969uE4jbJczlU+e1E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=vwewnkOBBy8+RnodEAMVvWrmDa3GEZnAtupJeYDVt3E4dh8zoRNOp1+yBGbkwOX/c Fgbw9r/UEVrVQ7HFlZQLxYTMS6bhoZd8YgaN65InU9PlW1m7F28WZXFuEjH8jizWdv 8Bn1m5eoMDhfkLNIjHim+7zwqR8p41fN5rX/rq3Y= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Mason , Jeff Layton , Chuck Lever Subject: [PATCH 5.15 106/935] SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow Date: Sat, 12 Sep 2026 08:52:16 +0200 Message-ID: <20260912065529.249770205@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065526.833703348@linuxfoundation.org> References: <20260912065526.833703348@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Mason commit 3f491306dcb673ff5e78e1044ba450c58978774e upstream. xdr_buf_trim() trims `len` bytes from the tail of an xdr_buf by walking the tail, pages, and head iovecs. Each per-section step uses min_t() so it never removes more bytes than that section holds, but the final accounting at the fix_len label subtracts the total bytes actually consumed from buf->len without any clamp: fix_len: buf->len -= (len - trim); When the caller has set buf->len to a value smaller than the sum of the iov_lens, (len - trim) can exceed buf->len and the unsigned subtraction wraps to near UINT_MAX. gss_krb5_unwrap_v2() reaches xdr_buf_trim() in exactly that state: buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip; buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip); xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip); buf->len is a small wire-derived value while the iov_lens are at page scale, so the per-section loops legitimately consume far more bytes than buf->len records. The wrapped buf->len then propagates as the authoritative stream bound into every downstream XDR decoder. Fix by clamping the decrement so buf->len bottoms out at zero: buf->len -= min_t(unsigned int, buf->len, len - trim); On the normal path where the iov_lens sum to buf->len, (len - trim) is always <= buf->len and the result is identical to before. No callers change behavior outside the underflow case. Fixes: 4c190e2f913f ("sunrpc: trim off trailing checksum before returning decrypted or integrity authenticated buffer") Cc: stable@vger.kernel.org Assisted-by: kres (claude-opus-4-7) Signed-off-by: Chris Mason Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260524010213.557424-4-cel@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/xdr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -1732,7 +1732,7 @@ void xdr_buf_trim(struct xdr_buf *buf, u trim -= cur; } fix_len: - buf->len -= (len - trim); + buf->len -= min_t(unsigned int, buf->len, len - trim); } EXPORT_SYMBOL_GPL(xdr_buf_trim);