[PATCH 1/2] pstore: fix buffer overflow while write offset equal to buffer size

[Liu Shuo]

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

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....@intel.com>
---
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 de272d4..ff7e3d4 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);

--
1.8.3.2



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