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fuse-uring: clear ent->fuse_req in commit_fetch error path

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fuse_uring_commit_fetch() error path called fuse_request_end(req) without
clearing ent->fuse_req when fuse_ring_ent_set_commit() fails. The
still-pending fuse_uring_send_in_task() task-work later dereferences the
dangling pointer through fuse_uring_prepare_send(), causing a
use-after-free.

End the request with fuse_uring_req_end(), which handles all conditions
already.

Annotation/edition by Bernd: The UAF should be fixed by other means already
and actually has to be avoided that way.
Just checking for ent->fuse_req == NULL in fuse_uring_send_in_task()
would be prone to race conditions, because if malicious userspace
would commit requests that have passed the NULL check, but are
in doing args copy, it would still trigger a use-after-free.
Setting ent->fuse_req = NULL in fuse_uring_commit_fetch() still
makes sense, though.

Reported-by: Shuvam Pandey <shuvampandey1@gmail.com>
Reported-by: Berkant Koc <me@berkoc.com>
Signed-off-by: Zhenghang Xiao <kipreyyy@gmail.com>
Signed-off-by: Bernd Schubert <bernd@bsbernd.com>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Zhenghang Xiao 2026-06-15 12:25:56 +02:00 committed by Miklos Szeredi
parent 8bbb2ad1f6
commit 7d87a5a284
1 changed files with 1 additions and 3 deletions
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4
fs/fuse/dev_uring.c
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@ -1003,9 +1003,7 @@ static int fuse_uring_commit_fetch(struct io_uring_cmd *cmd, int issue_flags,
pr_info_ratelimited("qid=%d commit_id %llu state %d",
queue->qid, commit_id, ent->state);
spin_unlock(&queue->lock);
req->out.h.error = err;
clear_bit(FR_SENT, &req->flags);
fuse_request_end(req);
fuse_uring_req_end(ent, req, err);
return err;
}