linux-kernel - [PATCH] fs: btrfs: Fix a possible null-pointer dereference in insert_inline

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Date:   Wed, 24 Jul 2019 10:11:32 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     clm@...com, josef@...icpanda.com, dsterba@...e.com
Cc:     linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] fs: btrfs: Fix a possible null-pointer dereference in insert_inline_extent()

In insert_inline_extent(), there is an if statement on line 181 to check
whether compressed_pages is NULL:
    if (compressed_size && compressed_pages)

When compressed_pages is NULL, compressed_pages is used on line 215:
    cpage = compressed_pages[i];

Thus, a possible null-pointer dereference may occur.

To fix this possible bug, compressed_pages is checked on line 214.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 fs/btrfs/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 1af069a9a0c7..19182272fbd8 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -211,7 +211,7 @@ static int insert_inline_extent(struct btrfs_trans_handle *trans,
 	if (compress_type != BTRFS_COMPRESS_NONE) {
 		struct page *cpage;
 		int i = 0;
-		while (compressed_size > 0) {
+		while (compressed_size > 0 && compressed_pages) {
 			cpage = compressed_pages[i];
 			cur_size = min_t(unsigned long, compressed_size,
 				       PAGE_SIZE);
-- 
2.17.0