From: Vincent Bernat <vincent@bernat.im>
Date: Sat, 15 Aug 2015 12:07:44 +0000 (+0200)
Subject: 9p: fix return code of read() when count is 0
X-Git-Tag: v4.3-rc1~67^2
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b5ac1fb2717e48177d3f73f9e4c9b556c0a24c6b;p=platform%2Fkernel%2Flinux-exynos.git

9p: fix return code of read() when count is 0

When reading 0 bytes from an empty file on a 9P filesystem, the return
code of read() was not 0 as expected due to an unitialized err variable.

Tested with this simple program:

    #include <assert.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <unistd.h>

    int main(int argc, const char **argv)
    {
        assert(argc == 2);
        char buffer[256];
        int fd = open(argv[1], O_RDONLY|O_NOCTTY);
        assert(fd >= 0);
        assert(read(fd, buffer, 0) == 0);
        return 0;
    }

Signed-off-by: Vincent Bernat <vincent@bernat.im>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
---

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 1ef16bd..3abc447 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -381,7 +381,7 @@ static ssize_t
 v9fs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
 	struct p9_fid *fid = iocb->ki_filp->private_data;
-	int ret, err;
+	int ret, err = 0;
 
 	p9_debug(P9_DEBUG_VFS, "count %zu offset %lld\n",
 		 iov_iter_count(to), iocb->ki_pos);