Re: [Patch v2] btrfs: use file_remove_suid() after i_mutex is held

From: Amerigo Wang
Date: Mon Jul 06 2009 - 05:10:46 EST


Tao Ma wrote:
Hi Amerigo,

Amerigo Wang wrote:
V1 -> V2:
Move kmalloc() before mutex_lock(), suggested by Arjan.

file_remove_suid() should be called with i_mutex held,
file_update_time() too. So move them after mutex_lock().

Plus, check the return value of kmalloc().

Signed-off-by: WANG Cong <amwang@xxxxxxxxxx>
Cc: Arjan <arjan@xxxxxxxxxxxxx>
Cc: Chris Mason <chris.mason@xxxxxxxxxx>
Cc: Yan Zheng <zheng.yan@xxxxxxxxxx>
Cc: Sven Wegener <sven.wegener@xxxxxxxxxxx>
Cc: Josef Bacik <jbacik@xxxxxxxxxx>
Cc: Jeff Mahoney <jeffm@xxxxxxxx>

---
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 7c3cd24..09ef5d6 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -944,14 +944,17 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
if (count == 0)
goto out_nolock;
+ pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
+ if (!pages)
+ goto out_nolock;
I guess you need to set err to -ENOMEM here so that the caller knows what's wrong. With your patch, this function just return 0(since num_written and err are both 0) with no error, and I guess it is worse than kernel BUG out when the NULL pages is used later.

Agree. Thanks, I will update it.

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