From mboxrd@z Thu Jan 1 00:00:00 1970 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 5E80CBA4F for ; Tue, 7 Mar 2023 19:07:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1D5CC433D2; Tue, 7 Mar 2023 19:07:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678216058; bh=ZONAirZ6zfNf1iTb0FxKJx91w3mgVP51sUbKEawi4b4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=f+qe44Hcx2CwFzWv0OzHyp+bOnmsHzld4+p60PNr1ffuTrcKd/41DsV5eemitn5px a8y1z7LJNsWVgVHr3QCRg6f76x/G61LM+OKKD2Ok+OV9fuSsk818r2ALjzOTLiUia0 BX5ClNkwalo2A1YM9zxhNcxTZdRGIYoWdbFw/MVs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gerald Schaefer , Heiko Carstens Subject: [PATCH 5.15 434/567] s390/extmem: return correct segment type in __segment_load() Date: Tue, 7 Mar 2023 18:02:50 +0100 Message-Id: <20230307165924.721618457@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230307165905.838066027@linuxfoundation.org> References: <20230307165905.838066027@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Gerald Schaefer commit 8c42dd78df148c90e48efff204cce38743906a79 upstream. Commit f05f62d04271f ("s390/vmem: get rid of memory segment list") reshuffled the call to vmem_add_mapping() in __segment_load(), which now overwrites rc after it was set to contain the segment type code. As result, __segment_load() will now always return 0 on success, which corresponds to the segment type code SEG_TYPE_SW, i.e. a writeable segment. This results in a kernel crash when loading a read-only segment as dcssblk block device, and trying to write to it. Instead of reshuffling code again, make sure to return the segment type on success, and also describe this rather delicate and unexpected logic in the function comment. Also initialize new segtype variable with invalid value, to prevent possible future confusion. Fixes: f05f62d04271 ("s390/vmem: get rid of memory segment list") Cc: # 5.9+ Signed-off-by: Gerald Schaefer Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens Signed-off-by: Greg Kroah-Hartman --- arch/s390/mm/extmem.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/arch/s390/mm/extmem.c +++ b/arch/s390/mm/extmem.c @@ -289,15 +289,17 @@ segment_overlaps_others (struct dcss_seg /* * real segment loading function, called from segment_load + * Must return either an error code < 0, or the segment type code >= 0 */ static int __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long *end) { unsigned long start_addr, end_addr, dummy; struct dcss_segment *seg; - int rc, diag_cc; + int rc, diag_cc, segtype; start_addr = end_addr = 0; + segtype = -1; seg = kmalloc(sizeof(*seg), GFP_KERNEL | GFP_DMA); if (seg == NULL) { rc = -ENOMEM; @@ -326,9 +328,9 @@ __segment_load (char *name, int do_nonsh seg->res_name[8] = '\0'; strlcat(seg->res_name, " (DCSS)", sizeof(seg->res_name)); seg->res->name = seg->res_name; - rc = seg->vm_segtype; - if (rc == SEG_TYPE_SC || - ((rc == SEG_TYPE_SR || rc == SEG_TYPE_ER) && !do_nonshared)) + segtype = seg->vm_segtype; + if (segtype == SEG_TYPE_SC || + ((segtype == SEG_TYPE_SR || segtype == SEG_TYPE_ER) && !do_nonshared)) seg->res->flags |= IORESOURCE_READONLY; /* Check for overlapping resources before adding the mapping. */ @@ -386,7 +388,7 @@ __segment_load (char *name, int do_nonsh out_free: kfree(seg); out: - return rc; + return rc < 0 ? rc : segtype; } /*