[Devel] [PATCH RHEL7 COMMIT] fuse: Check for req->ff in fuse_request_queue_background()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-957.12.1.vz7.95.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-957.12.1.vz7.95.3
------>
commit 6b281cfd6a4f55e20e83ffbe403c2b5f3ff701fb
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Mon May 6 15:22:55 2019 +0300

    fuse: Check for req->ff in fuse_request_queue_background()
    
    A request may have no ff assigned, and such the requests
    can't be dropped immediately. E.g.:
    
    [    9.238630]  [<ffffffffb80530d0>] fuse_request_queue_background+0x1d0/0x1e0
    [    9.243064]  [<ffffffffb805312e>] fuse_request_send_background+0x4e/0xa0
    [    9.247300]  [<ffffffffb8061a71>] fuse_fill_super+0x5f1/0x620
    [    9.253878]  [<ffffffffb8061480>] ? fuse_iget+0x1f0/0x1f0
    [    9.261936]  [<ffffffffb7ea035f>] mount_nodev+0x4f/0xb0
    [    9.266502]  [<ffffffffb805fb3c>] fuse_mount+0x1c/0x90
    [    9.271076]  [<ffffffffb7ea0f5a>] mount_fs+0x1a/0xc0
    [    9.275472]  [<ffffffffb7ebec47>] vfs_kern_mount+0x67/0x110
    [    9.282489]  [<ffffffffb7ec15e1>] do_mount+0x1b1/0xc90
    [    9.290380]  [<ffffffffb7ec1350>] ? copy_mount_options+0xc0/0x170
    [    9.295603]  [<ffffffffb7ec2403>] SyS_mount+0x83/0xd0
    [    9.300777]  [<ffffffffb874adc8>] system_call_fastpath+0x22/0x27
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 fs/fuse/dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 1958c6e33d79..f9e33a504c70 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -612,7 +612,7 @@ bool fuse_request_queue_background(struct fuse_conn *fc, struct fuse_req *req)
 	}
 	__set_bit(FR_ISREPLY, &req->flags);
 	spin_lock(&fc->bg_lock);
-	if (unlikely(test_bit(FUSE_S_FAIL_IMMEDIATELY, &req->ff->ff_state)))
+	if (req->ff && unlikely(test_bit(FUSE_S_FAIL_IMMEDIATELY, &req->ff->ff_state)))
 		req->out.h.error = -EIO;
 	else if (likely(fc->connected)) {
 		fc->num_background++;