[PATCH 4.4 109/160] fuse: Fix use-after-free in fuse_dev_do_write()

From: Greg Kroah-Hartman
Date: Mon Nov 19 2018 - 12:02:19 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>

commit d2d2d4fb1f54eff0f3faa9762d84f6446a4bc5d0 upstream.

After we found req in request_find() and released the lock,
everything may happen with the req in parallel:

cpu0 cpu1
fuse_dev_do_write() fuse_dev_do_write()
req = request_find(fpq, ...) ...
spin_unlock(&fpq->lock) ...
... req = request_find(fpq, oh.unique)
... spin_unlock(&fpq->lock)
queue_interrupt(&fc->iq, req); ...
... ...
... ...
request_end(fc, req);
fuse_put_request(fc, req);
... queue_interrupt(&fc->iq, req);


Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Fixes: 46c34a348b0a ("fuse: no fc->lock for pqueue parts")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.2
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
fs/fuse/dev.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1924,16 +1924,20 @@ static ssize_t fuse_dev_do_write(struct

/* Is it an interrupt reply? */
if (req->intr_unique == oh.unique) {
+ __fuse_get_request(req);
spin_unlock(&fpq->lock);

err = -EINVAL;
- if (nbytes != sizeof(struct fuse_out_header))
+ if (nbytes != sizeof(struct fuse_out_header)) {
+ fuse_put_request(fc, req);
goto err_finish;
+ }

if (oh.error == -ENOSYS)
fc->no_interrupt = 1;
else if (oh.error == -EAGAIN)
queue_interrupt(&fc->iq, req);
+ fuse_put_request(fc, req);

fuse_copy_finish(cs);
return nbytes;