From 54c318d5004af458616ac91b685d2408c184435d Mon Sep 17 00:00:00 2001 From: Kirill Tkhai Date: Tue, 25 Sep 2018 12:28:55 +0300 Subject: [PATCH] fuse: Fix use-after-free in fuse_dev_do_read() BugLink: https://bugs.launchpad.net/bugs/1824553 We may pick freed req in this way: [cpu0] [cpu1] fuse_dev_do_read() fuse_dev_do_write() list_move_tail(&req->list, ...); ... spin_unlock(&fpq->lock); ... ... request_end(fc, req); ... fuse_put_request(fc, req); if (test_bit(FR_INTERRUPTED, ...)) queue_interrupt(fiq, req); Fix that by keeping req alive until we finish all manipulations. Reported-by: syzbot+4e975615ca01f2277bdd@syzkaller.appspotmail.com Signed-off-by: Kirill Tkhai Signed-off-by: Miklos Szeredi Fixes: 46c34a348b0a ("fuse: no fc->lock for pqueue parts") Cc: # v4.2 (cherry picked from commit bc78abbd55dd28e2287ec6d6502b842321a17c87) Signed-off-by: Andrea Righi Acked-by: Stefan Bader Acked-by: Kleber Sacilotto de Souza Signed-off-by: Kleber Sacilotto de Souza --- fs/fuse/dev.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index d925d81e1525..8ce3f1bead24 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1316,12 +1316,14 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, goto out_end; } list_move_tail(&req->list, &fpq->processing); + __fuse_get_request(req); spin_unlock(&fpq->lock); set_bit(FR_SENT, &req->flags); /* matches barrier in request_wait_answer() */ smp_mb__after_atomic(); if (test_bit(FR_INTERRUPTED, &req->flags)) queue_interrupt(fiq, req); + fuse_put_request(fc, req); return reqsize; -- 2.39.2