[PATCH] fuse:send filep uid as part of fuse write req

[Chakra Divi <chakragithub@gmail.com>]

In current code in fuse write request current_fsuid is sent,
however this creates an issue in sudo execution context.
Changes to consider uid and gid from file struture pointer
that is created as part of open file instead of current_fsuid,gid

Steps to reproduce the issue:
1) create user1 and user2
2) create a file1 with user1 on fusemount
3) change the file1 permissions to 600
4) execute the following command
user1@linux# sudo -u user2 whoami >> /fusemnt/file1
Here write fails with permission denied error

on nfs and ext4 - above use case is working, but on fuse
its failing

Signed-off-by: Chakra Divi <chakragithub@gmail.com>
---
 fs/fuse/file.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 5ae2828..e1d223c 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1134,6 +1134,7 @@ static ssize_t fuse_perform_write(struct kiocb *iocb,
 	struct inode *inode = mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct file *file = iocb->ki_filp;
 	int err = 0;
 	ssize_t res = 0;
 
@@ -1150,6 +1151,9 @@ static ssize_t fuse_perform_write(struct kiocb *iocb,
 		if (IS_ERR(req)) {
 			err = PTR_ERR(req);
 			break;
+		} else {
+			req->in.h.uid = file->f_cred->uid.val;
+			req->in.h.gid = file->f_cred->gid.val;
 		}
 
 		count = fuse_fill_write_pages(req, mapping, ii, pos);
-- 
2.7.4