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fuse: fix use after free in fuse_read_interrupt()

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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@xiaomi.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2021-08-04 13:22:58 +02:00
parent e73f0f0ee7
commit e1e71c1688
1 changed files with 2 additions and 2 deletions
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4
fs/fuse/dev.c
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@ -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);