From: Li RongQing <roy.qing...@gmail.com>

It is impossible that csum_size is larger than sizeof(long), but the codes
still add the handler for this condition, like allocate new memory, for
extension. If it becomes true someday, copying csum_size size memory to local
32bit variable found and val will overflow these two variables.

Fix it by returning the max 4 byte checksum, and print the csum_size

Signed-off-by: Li RongQing <roy.qing...@gmail.com>
---
 fs/btrfs/disk-io.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index a1d36e6..d9b52ac 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -295,14 +295,17 @@ static int csum_tree_block(struct btrfs_root *root, 
struct extent_buffer *buf,
                if (memcmp_extent_buffer(buf, result, 0, csum_size)) {
                        u32 val;
                        u32 found = 0;
+
+                       csum_size = min_t(u16, csum_size, sizeof(u32));
                        memcpy(&found, result, csum_size);
 
                        read_extent_buffer(buf, &val, 0, csum_size);
                        printk_ratelimited(KERN_INFO
                                "BTRFS: %s checksum verify failed on %llu 
wanted %X found %X "
-                               "level %d\n",
+                               "level %d checksum size %d\n",
                                root->fs_info->sb->s_id, buf->start,
-                               val, found, btrfs_header_level(buf));
+                               val, found, btrfs_header_level(buf), csum_size);
+
                        if (result != (char *)&inline_result)
                                kfree(result);
                        return 1;
-- 
1.7.10.4

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