linux-kernel - [PATCH 13/18] pstore: Allocate records on heap instead of stack

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Date:   Mon,  6 Mar 2017 13:55:27 -0800
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Nobuhiro Iwamatsu <nobuhiro.iwamatsu.kw@...achi.com>,
        Qiuxu Zhuo <qiuxu.zhuo@...el.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
        Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>,
        Daniel Axtens <dja@...ens.net>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Geliang Tang <geliangtang@....com>,
        linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-doc@...r.kernel.org
Subject: [PATCH 13/18] pstore: Allocate records on heap instead of stack

In preparation for handling records off to pstore_mkfile(), allocate the
record instead of reusing stack. This still always frees the record,
though, since pstore_mkfile() isn't yet keeping it.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/pstore/platform.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index d897e2f11b6a..072326625629 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -818,8 +818,7 @@ static void decompress_record(struct pstore_record *record)
 void pstore_get_records(int quiet)
 {
 	struct pstore_info *psi = psinfo;
-	struct pstore_record	record = { .psi = psi, };
-	int			failed = 0, rc;
+	int failed = 0;
 
 	if (!psi)
 		return;
@@ -833,19 +832,34 @@ void pstore_get_records(int quiet)
 	 * may reallocate record.buf. On success, pstore_mkfile() will keep
 	 * the record.buf, so free it only on failure.
 	 */
-	while ((record.size = psi->read(&record)) > 0) {
-		decompress_record(&record);
-		rc = pstore_mkfile(&record);
+	for (;;) {
+		struct pstore_record *record;
+		int rc;
+
+		record = kzalloc(sizeof(*record), GFP_KERNEL);
+		if (!record) {
+			pr_err("out of memory creating record\n");
+			break;
+		}
+		record->psi = psi;
+
+		record->size = psi->read(record);
+
+		/* No more records left in backend? */
+		if (record->size <= 0)
+			break;
+
+		decompress_record(record);
+		rc = pstore_mkfile(record);
 		if (rc) {
 			/* pstore_mkfile() did not take buf, so free it. */
-			kfree(record.buf);
+			kfree(record->buf);
 			if (rc != -EEXIST || !quiet)
 				failed++;
 		}
 
 		/* Reset for next record. */
-		memset(&record, 0, sizeof(record));
-		record.psi = psi;
+		kfree(record);
 	}
 	if (psi->close)
 		psi->close(psi);
-- 
2.7.4