linux-kernel - [PATCH] fs: affs: fix a NULL pointer dereference

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Date:   Fri, 15 Mar 2019 02:42:44 -0500
From:   Kangjie Lu <kjlu@....edu>
To:     kjlu@....edu
Cc:     pakki001@....edu, David Sterba <dsterba@...e.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] fs: affs: fix a NULL pointer dereference

If affs_bread fails, do not use ext_bh to avoid NULL pointer
 dereference

Signed-off-by: Kangjie Lu <kjlu@....edu>
---
 fs/affs/file.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/affs/file.c b/fs/affs/file.c
index a85817f54483..29cbc8eda085 100644
--- a/fs/affs/file.c
+++ b/fs/affs/file.c
@@ -941,8 +941,10 @@ affs_truncate(struct inode *inode)
 		size = AFFS_SB(sb)->s_hashsize;
 		if (size > blkcnt - blk)
 			size = blkcnt - blk;
-		for (i = 0; i < size; i++, blk++)
-			affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
+		if (ext_bh) {
+			for (i = 0; i < size; i++, blk++)
+				affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
+		}
 		affs_free_block(sb, ext_key);
 		ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);
 		affs_brelse(ext_bh);
-- 
2.17.1