From 7fabaf303458fcabb694999d6fa772cc13d4e217 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 9 Nov 2018 15:52:16 +0100 Subject: [PATCH 1/3] fuse: fix leaked notify reply fuse_request_send_notify_reply() may fail if the connection was reset for some reason (e.g. fs was unmounted). Don't leak request reference in this case. Besides leaking memory, this resulted in fc->num_waiting not being decremented and hence fuse_wait_aborted() left in a hanging and unkillable state. Fixes: 2d45ba381a74 ("fuse: add retrieve request") Fixes: b8f95e5d13f5 ("fuse: umount should wait for all requests") Reported-and-tested-by: syzbot+6339eda9cb4ebbc4c37b@syzkaller.appspotmail.com Signed-off-by: Miklos Szeredi Cc: #v2.6.36 --- fs/fuse/dev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index ae813e609932..6fe330cc9709 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1768,8 +1768,10 @@ static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode, req->in.args[1].size = total_len; err = fuse_request_send_notify_reply(fc, req, outarg->notify_unique); - if (err) + if (err) { fuse_retrieve_end(fc, req); + fuse_put_request(fc, req); + } return err; } From 2d84a2d19b6150c6dbac1e6ebad9c82e4c123772 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 9 Nov 2018 15:52:16 +0100 Subject: [PATCH 2/3] fuse: fix possibly missed wake-up after abort In current fuse_drop_waiting() implementation it's possible that fuse_wait_aborted() will not be woken up in the unlikely case that fuse_abort_conn() + fuse_wait_aborted() runs in between checking fc->connected and calling atomic_dec(&fc->num_waiting). Do the atomic_dec_and_test() unconditionally, which also provides the necessary barrier against reordering with the fc->connected check. The explicit smp_mb() in fuse_wait_aborted() is not actually needed, since the spin_unlock() in fuse_abort_conn() provides the necessary RELEASE barrier after resetting fc->connected. However, this is not a performance sensitive path, and adding the explicit barrier makes it easier to document. Signed-off-by: Miklos Szeredi Fixes: b8f95e5d13f5 ("fuse: umount should wait for all requests") Cc: #v4.19 --- fs/fuse/dev.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 6fe330cc9709..a5e516a40e7a 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -165,9 +165,13 @@ static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background) static void fuse_drop_waiting(struct fuse_conn *fc) { - if (fc->connected) { - atomic_dec(&fc->num_waiting); - } else if (atomic_dec_and_test(&fc->num_waiting)) { + /* + * lockess check of fc->connected is okay, because atomic_dec_and_test() + * provides a memory barrier mached with the one in fuse_wait_aborted() + * to ensure no wake-up is missed. + */ + if (atomic_dec_and_test(&fc->num_waiting) && + !READ_ONCE(fc->connected)) { /* wake up aborters */ wake_up_all(&fc->blocked_waitq); } @@ -2221,6 +2225,8 @@ EXPORT_SYMBOL_GPL(fuse_abort_conn); void fuse_wait_aborted(struct fuse_conn *fc) { + /* matches implicit memory barrier in fuse_drop_waiting() */ + smp_mb(); wait_event(fc->blocked_waitq, atomic_read(&fc->num_waiting) == 0); } From ebacb81273599555a7a19f7754a1451206a5fc4f Mon Sep 17 00:00:00 2001 From: Lukas Czerner Date: Fri, 9 Nov 2018 14:51:46 +0100 Subject: [PATCH 3/3] fuse: fix use-after-free in fuse_direct_IO() In async IO blocking case the additional reference to the io is taken for it to survive fuse_aio_complete(). In non blocking case this additional reference is not needed, however we still reference io to figure out whether to wait for completion or not. This is wrong and will lead to use-after-free. Fix it by storing blocking information in separate variable. This was spotted by KASAN when running generic/208 fstest. Signed-off-by: Lukas Czerner Reported-by: Zorro Lang Signed-off-by: Miklos Szeredi Fixes: 744742d692e3 ("fuse: Add reference counting for fuse_io_priv") Cc: # v4.6 --- fs/fuse/file.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index cc2121b37bf5..b52f9baaa3e7 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2924,10 +2924,12 @@ fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter) } if (io->async) { + bool blocking = io->blocking; + fuse_aio_complete(io, ret < 0 ? ret : 0, -1); /* we have a non-extending, async request, so return */ - if (!io->blocking) + if (!blocking) return -EIOCBQUEUED; wait_for_completion(&wait);