[PATCH 3.10 247/319] pstore: Fix buffer overflow while write offset equal to buffer size

Willy Tarreau
2017-02-05T19:52:46Z

From: Liu ShuoX <shuox.liu@intel.com>

commit 017321cf390045dd4c4afc4a232995ea50bcf66d upstream.

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>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
fs/pstore/ram_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index bda61a7..0b367ef 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);

--
2.8.0.rc2.1.gbe9624a