From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794047593; b=dHgiJ3kbp4W0mAy8bsC4a+eqU7vcj1+C4UrpscLMYVhAZYDANwVAesZVaR539neA3D1K xQi65lmlPWXaJ1LMf7hpmsEOzn9NY2U4UNduD5mK74aCmBa+TXIfr8P9IRYKsDkOjeF7l P49Mv8x5nDmMrEsCwM/0sEVQY0Ja4nRfXWZbrUCQ+froYH96ecjDZzZjkBhBHMmqbQiOq LcF1IyPkGBHH1AQ/j+KefyHLyuAduXfI6EHaty/N8Q8Hs+yYdMC9bv2d5UA8lgXVw+m5G mFGHs9Q+evy6jDAZNWG2oEsrH+pbsartK/jTqc1+KoAUe92USckCPHBQdeZG6JEP/Lg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047593; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=/fiU2r2Vc8QJa3bfBzIKxH70rvX3zekiNT9tijrq5Nw=; b=wIL3CnNnZFLUvJR1pu5ZziYf0ka/LwAasIGbVM7PHgR+0S++bMfINOqUAHKrhQ3Mn1Cl yT6ZzfJN2fBMXHxvSjCzoSAev7SREtzjxEJ6Y8AzrkguKc11SgO9KR/aH5mE0e4GQEMnv wjMel2gd67OHYOka6L9OnIVHN1xSuDNKirmDCS7ttJGaeuuzj/OCkBFk/KgOFI3AnURmJ bX2nYX/1o2uyqmQEj+Eg4fYrIEFQAsHG8DDLpXfG9isT/wzQJqu4DfwctUJBdVLD/T/DA +Vg4KkrSyOUwfxDyhhR0SbMb3fO5Akc/O0OlDDUEJdvLprOh9divNz/dxttFykbk7JA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=J9psMVY2; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E2B71606A326 for ; Sat, 7 Nov 2026 10:33:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=J9psMVY2 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0BEE81F0089F; Sat, 7 Nov 2026 10:33:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047592; bh=/fiU2r2Vc8QJa3bfBzIKxH70rvX3zekiNT9tijrq5Nw=; h=From:To:Cc:Subject:Date; b=J9psMVY2jcDQmFiZ/8GhIpqgvdXBAOkEVafWFT227ob78iUHueGb+5NRl0yhnIzcg 4+jWbrPmOQKZT6vTJQIW+roaU1i6w3NCcqQ847HeO4BDoc/OaFCRkAEipkVUFslobo ykIp2748bXOrp5yXcsznDYdD5W3h/MEljB/3+/p9yLYxy1ir8G1/bHuQPoq+IBywLg 7vf1BYPsAcJcdGok9rqcqXhnjABrHSzwhxO8qjjBAvQ1wVB+nIDZZgJ1Fgv64/dC+k ksRD2yv13h8nPjMu84xYPMAZpqFmCEsBRNVydgbvc7Wy/KNLmqW9CdeTwuJEe8mGo+ rRDhqyEzy4Nvw== From: Sasha Levin To: yhlee@isslab.korea.ac.kr, jgross@suse.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] xen/scsifront: check for a NULL shadow entry on a backend response" failed to apply to 6.6-stable tree Date: Sat, 7 Nov 2026 05:33:11 -0500 Message-ID: <20261107053310-failed-6.6-992df081bc88@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 992df081bc8878d11e1eb5ae4a609910fd35c62b # git commit -s git send-email --to '' --in-reply-to '20261107053310-failed-6.6-992df081bc88@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 992df081bc8878d11e1eb5ae4a609910fd35c62b Mon Sep 17 00:00:00 2001 From: Yehyeong Lee Date: Mon, 5 Oct 2026 21:35:54 +0900 Subject: [PATCH] xen/scsifront: check for a NULL shadow entry on a backend response scsifront_do_response() validates the rqid in a backend response against VSCSIIF_MAX_REQS before using it to index info->shadow[], but then dereferences the entry to test ->inflight without checking that the slot is populated. Shadow slots are NULL before a command is submitted (the host private area is zeroed at allocation) and are reset to NULL in _scsifront_put_rqid() once a request completes, so an in-range rqid that does not correspond to an outstanding request makes the frontend dereference a NULL pointer. A malicious or buggy backend can thus crash the guest by returning a response whose rqid is in range but not in flight -- for example a spurious response before any command has been issued, or a duplicate of one already completed. The ring has only VSCSIIF_MAX_REQS (16) slots, so before the first command every in-range rqid selects a NULL slot. Reject a response whose shadow slot is not populated. Fixes: 6d1c2f48f3fc ("xen/scsifront: harden driver against malicious backend") Cc: stable@vger.kernel.org Signed-off-by: Yehyeong Lee Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Message-ID: <20261005123555.253995-1-yhlee@isslab.korea.ac.kr> --- drivers/scsi/xen-scsifront.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c index f86a47056ea8c..9d7e12e400896 100644 --- a/drivers/scsi/xen-scsifront.c +++ b/drivers/scsi/xen-scsifront.c @@ -367,6 +367,7 @@ static void scsifront_do_response(struct vscsifrnt_info *info, struct vscsifrnt_shadow *shadow; if (ring_rsp->rqid >= VSCSIIF_MAX_REQS || + !info->shadow[ring_rsp->rqid] || !info->shadow[ring_rsp->rqid]->inflight) { scsifront_set_error(info, "illegal rqid returned by backend!"); return; -- 2.53.0