From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
[ Upstream commit e1e71c168813564be0f6ea3d6740a059ca42d177 ]
There is a potential race between fuse_read_interrupt() and
fuse_request_end().
TASK1
in fuse_read_interrupt(): delete req->intr_entry (while holding
fiq->lock)
TASK2
in fuse_request_end(): req->intr_entry is empty -> skip fiq->lock
wake up TASK3
TASK3
request is freed
TASK1
in fuse_read_interrupt(): dereference req->in.h.unique ***BAM***
Fix by always grabbing fiq->lock if the request was ever interrupted
(FR_INTERRUPTED set) thereby serializing with concurrent
fuse_read_interrupt() calls.
FR_INTERRUPTED is set before the request is queued on fiq->interrupts.
Dequeing the request is done with list_del_init() but FR_INTERRUPTED is not
cleared in this case.
Reported-by: lijiazi <lijiazi@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/fuse/dev.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 1c8f79b3dd06..dde341a6388a 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -288,10 +288,10 @@ void fuse_request_end(struct fuse_req *req)
/*
* test_and_set_bit() implies smp_mb() between bit
- * changing and below intr_entry check. Pairs with
+ * changing and below FR_INTERRUPTED check. Pairs with
* smp_mb() from queue_interrupt().
*/
- if (!list_empty(&req->intr_entry)) {
+ if (test_bit(FR_INTERRUPTED, &req->flags)) {
spin_lock(&fiq->lock);
list_del_init(&req->intr_entry);
spin_unlock(&fiq->lock);
--
2.30.2
