linux-kernel - [PATCH 2/3] pstore: Check for prz allocation in walker

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Date:   Mon, 13 Feb 2017 10:33:42 -0800
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Brian Norris <briannorris@...omium.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>
Subject: [PATCH 2/3] pstore: Check for prz allocation in walker

Instead of needing additional checks in callers for unallocated przs,
perform the check in the walker, which gives us a more universal way to
handle the situation.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/pstore/ram.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 1d887efaaf71..11f918d34b1e 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -133,7 +133,8 @@ ramoops_get_next_prz(struct persistent_ram_zone *przs[], uint *c, uint max,
 	struct persistent_ram_zone *prz;
 	int i = (*c)++;
 
-	if (i >= max)
+	/* Give up if we never existed or have hit the end. */
+	if (!przs || i >= max)
 		return NULL;
 
 	prz = przs[i];
@@ -280,7 +281,7 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type,
 					   1, id, type, PSTORE_TYPE_PMSG, 0);
 
 	/* ftrace is last since it may want to dynamically allocate memory. */
-	if (!prz_ok(prz) && cxt->fprzs) {
+	if (!prz_ok(prz)) {
 		if (!(cxt->flags & RAMOOPS_FLAG_FTRACE_PER_CPU)) {
 			prz = ramoops_get_next_prz(cxt->fprzs,
 					&cxt->ftrace_read_cnt, 1, id, type,
-- 
2.7.4