fuse: initialize the flock flag in fuse_file on allocation

fuse: initialize the flock flag in fuse_file on allocation

Before the patch, the flock flag could remain uninitialized for the
lifespan of the fuse_file allocation. Unless set to true in
fuse_file_flock(), it would remain in an indeterminate state until read in
an if statement in fuse_release_common(). This could consequently lead to
taking an unexpected branch in the code.

The bug was discovered by a runtime instrumentation designed to detect use
of uninitialized memory in the kernel.

Signed-off-by: Mateusz Jurczyk <[email protected]>
Fixes: 37fb3a30b462 ("fuse: fix flock")
Cc: <[email protected]> # v3.1+
Signed-off-by: Miklos Szeredi <[email protected]>