Patch "ksmbd: fix race condition with fp" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    ksmbd: fix race condition with fp

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ksmbd-fix-race-condition-with-fp.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b57845f40f0bba8a4b103274bc0d12a861038b48
Author: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Date:   Sun Dec 31 16:13:04 2023 +0900

    ksmbd: fix race condition with fp
    
    [ Upstream commit 5a7ee91d1154f35418367a6eaae74046fd06ed89 ]
    
    fp can used in each command. If smb2_close command is coming at the
    same time, UAF issue can happen by race condition.
    
                               Time
                                +
    Thread A                    | Thread B1 B2 .... B5
    smb2_open                   | smb2_close
                                |
     __open_id                  |
       insert fp to file_table  |
                                |
                                |   atomic_dec_and_test(&fp->refcount)
                                |   if fp->refcount == 0, free fp by kfree.
     // UAF!                    |
     use fp                     |
                                +
    This patch add f_state not to use freed fp is used and not to free fp in
    use.
    
    Reported-by: luosili <rootlab@xxxxxxxxxx>
    Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
    Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index 42697ea86d47b..d5bf1f480700a 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -3370,8 +3370,10 @@ int smb2_open(struct ksmbd_work *work)
 	}
 	ksmbd_revert_fsids(work);
 err_out1:
-	if (!rc)
+	if (!rc) {
+		ksmbd_update_fstate(&work->sess->file_table, fp, FP_INITED);
 		rc = ksmbd_iov_pin_rsp(work, (void *)rsp, iov_len);
+	}
 	if (rc) {
 		if (rc == -EINVAL)
 			rsp->hdr.Status = STATUS_INVALID_PARAMETER;
diff --git a/fs/smb/server/vfs_cache.c b/fs/smb/server/vfs_cache.c
index 94ad8fa07b46e..f600279b0a9ee 100644
--- a/fs/smb/server/vfs_cache.c
+++ b/fs/smb/server/vfs_cache.c
@@ -332,6 +332,9 @@ static void __ksmbd_close_fd(struct ksmbd_file_table *ft, struct ksmbd_file *fp)
 
 static struct ksmbd_file *ksmbd_fp_get(struct ksmbd_file *fp)
 {
+	if (fp->f_state != FP_INITED)
+		return NULL;
+
 	if (!atomic_inc_not_zero(&fp->refcount))
 		return NULL;
 	return fp;
@@ -381,15 +384,20 @@ int ksmbd_close_fd(struct ksmbd_work *work, u64 id)
 		return 0;
 
 	ft = &work->sess->file_table;
-	read_lock(&ft->lock);
+	write_lock(&ft->lock);
 	fp = idr_find(ft->idr, id);
 	if (fp) {
 		set_close_state_blocked_works(fp);
 
-		if (!atomic_dec_and_test(&fp->refcount))
+		if (fp->f_state != FP_INITED)
 			fp = NULL;
+		else {
+			fp->f_state = FP_CLOSED;
+			if (!atomic_dec_and_test(&fp->refcount))
+				fp = NULL;
+		}
 	}
-	read_unlock(&ft->lock);
+	write_unlock(&ft->lock);
 
 	if (!fp)
 		return -EINVAL;
@@ -569,6 +577,7 @@ struct ksmbd_file *ksmbd_open_fd(struct ksmbd_work *work, struct file *filp)
 	fp->tcon		= work->tcon;
 	fp->volatile_id		= KSMBD_NO_FID;
 	fp->persistent_id	= KSMBD_NO_FID;
+	fp->f_state		= FP_NEW;
 	fp->f_ci		= ksmbd_inode_get(fp);
 
 	if (!fp->f_ci) {
@@ -590,6 +599,14 @@ struct ksmbd_file *ksmbd_open_fd(struct ksmbd_work *work, struct file *filp)
 	return ERR_PTR(ret);
 }
 
+void ksmbd_update_fstate(struct ksmbd_file_table *ft, struct ksmbd_file *fp,
+			 unsigned int state)
+{
+	write_lock(&ft->lock);
+	fp->f_state = state;
+	write_unlock(&ft->lock);
+}
+
 static int
 __close_file_table_ids(struct ksmbd_file_table *ft,
 		       struct ksmbd_tree_connect *tcon,
diff --git a/fs/smb/server/vfs_cache.h b/fs/smb/server/vfs_cache.h
index fcb13413fa8d9..03d0bf941216f 100644
--- a/fs/smb/server/vfs_cache.h
+++ b/fs/smb/server/vfs_cache.h
@@ -60,6 +60,12 @@ struct ksmbd_inode {
 	__le32				m_fattr;
 };
 
+enum {
+	FP_NEW = 0,
+	FP_INITED,
+	FP_CLOSED
+};
+
 struct ksmbd_file {
 	struct file			*filp;
 	u64				persistent_id;
@@ -98,6 +104,7 @@ struct ksmbd_file {
 	/* if ls is happening on directory, below is valid*/
 	struct ksmbd_readdir_data	readdir_data;
 	int				dot_dotdot[2];
+	unsigned int			f_state;
 };
 
 static inline void set_ctx_actor(struct dir_context *ctx,
@@ -142,6 +149,8 @@ int ksmbd_close_inode_fds(struct ksmbd_work *work, struct inode *inode);
 int ksmbd_init_global_file_table(void);
 void ksmbd_free_global_file_table(void);
 void ksmbd_set_fd_limit(unsigned long limit);
+void ksmbd_update_fstate(struct ksmbd_file_table *ft, struct ksmbd_file *fp,
+			 unsigned int state);
 
 /*
  * INODE hash




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