[PATCH 4.1 63/78] 9p: ensure err is initialized to 0 in p9_client_read/write

Greg Kroah-Hartman
2015-09-11T22:51:28Z

From: Vincent Bernat <vincent@bernat.im>

commit 999b8b88c6060adf7a9b7907740ae86ace65291e upstream.

Some use of those functions were providing unitialized values to those
functions. Notably, when reading 0 bytes from an empty file on a 9P
filesystem, the return code of read() was not 0.

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: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/9p/client.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1541,6 +1541,7 @@ p9_client_read(struct p9_fid *fid, u64 o
struct p9_client *clnt = fid->clnt;
struct p9_req_t *req;
int total = 0;
+ *err = 0;

p9_debug(P9_DEBUG_9P, ">>> TREAD fid %d offset %llu %d\n",
fid->fid, (unsigned long long) offset, (int)iov_iter_count(to));
@@ -1616,6 +1617,7 @@ p9_client_write(struct p9_fid *fid, u64
struct p9_client *clnt = fid->clnt;
struct p9_req_t *req;
int total = 0;
+ *err = 0;

p9_debug(P9_DEBUG_9P, ">>> TWRITE fid %d offset %llu count %zd\n",
fid->fid, (unsigned long long) offset,