From: Liu ShuoX <shuox.liu@intel.com>
Date: Wed, 12 Mar 2014 13:24:44 +0000 (+0800)
Subject: pstore: Fix buffer overflow while write offset equal to buffer size
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=017321cf390045dd4c4afc4a232995ea50bcf66d;p=linux-beck.git

pstore: Fix buffer overflow while write offset equal to buffer size

In case new offset is equal to prz->buffer_size, it won't wrap at this
time and will return old(overflow) value next time.

Signed-off-by: Liu ShuoX <shuox.liu@intel.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
---

diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index de272d426763..ff7e3d4df5a1 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -54,7 +54,7 @@ static size_t buffer_start_add_atomic(struct persistent_ram_zone *prz, size_t a)
 	do {
 		old = atomic_read(&prz->buffer->start);
 		new = old + a;
-		while (unlikely(new > prz->buffer_size))
+		while (unlikely(new >= prz->buffer_size))
 			new -= prz->buffer_size;
 	} while (atomic_cmpxchg(&prz->buffer->start, old, new) != old);
 
@@ -91,7 +91,7 @@ static size_t buffer_start_add_locked(struct persistent_ram_zone *prz, size_t a)
 
 	old = atomic_read(&prz->buffer->start);
 	new = old + a;
-	while (unlikely(new > prz->buffer_size))
+	while (unlikely(new >= prz->buffer_size))
 		new -= prz->buffer_size;
 	atomic_set(&prz->buffer->start, new);