linux-kernel - Re: [PATCH] io_uring: fix filename leak in __io_openat

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Message-ID: <dc51a709-e404-4515-8023-3597c376aff5@kernel.dk>
Date: Wed, 24 Dec 2025 11:01:55 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Prithvi Tambewagh <activprithvi@...il.com>
Cc: io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
 brauner@...nel.org, jack@...e.cz, viro@...iv.linux.org.uk,
 linux-fsdevel@...r.kernel.org, linux-kernel-mentees@...ts.linux.dev,
 skhan@...uxfoundation.org, david.hunter.linux@...il.com, khalid@...nel.org,
 syzbot+00e61c43eb5e4740438f@...kaller.appspotmail.com, stable@...r.kernel.org
Subject: Re: [PATCH] io_uring: fix filename leak in __io_openat_prep()

On 12/24/25 9:42 AM, Prithvi Tambewagh wrote:
> __io_openat_prep() allocates a struct filename using getname(), but
> it isn't freed in case the present file is installed in the fixed file
> table and simultaneously, it has the flag O_CLOEXEC set in the
> open->how.flags field.
> 
> This is an erroneous condition, since for a file installed in the fixed
> file table, it won't be installed in the normal file table, due to which
> the file cannot support close on exec. Earlier, the code just returned
> -EINVAL error code for this condition, however, the memory allocated for
> that struct filename wasn't freed, resulting in a memory leak.
> 
> Hence, the case of file being installed in the fixed file table as well
> as having O_CLOEXEC flag in open->how.flags set, is adressed by using
> putname() to release the memory allocated to the struct filename, then
> setting the field open->filename to NULL, and after that, returning
> -EINVAL.
> 
> Reported-by: syzbot+00e61c43eb5e4740438f@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=00e61c43eb5e4740438f
> Tested-by: syzbot+00e61c43eb5e4740438f@...kaller.appspotmail.com
> Cc: stable@...r.kernel.org
> Signed-off-by: Prithvi Tambewagh <activprithvi@...il.com>
> ---
>  io_uring/openclose.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/io_uring/openclose.c b/io_uring/openclose.c
> index bfeb91b31bba..fc190a3d8112 100644
> --- a/io_uring/openclose.c
> +++ b/io_uring/openclose.c
> @@ -75,8 +75,11 @@ static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
>  	}
>  
>  	open->file_slot = READ_ONCE(sqe->file_index);
> -	if (open->file_slot && (open->how.flags & O_CLOEXEC))
> +	if (open->file_slot && (open->how.flags & O_CLOEXEC)) {
> +		putname(open->filename);
> +		open->filename = NULL;
>  		return -EINVAL;
> +	}
>  
>  	open->nofile = rlimit(RLIMIT_NOFILE);
>  	req->flags |= REQ_F_NEED_CLEANUP;

You can probably fix it similarly by just having REQ_F_NEED_CLEANUP set
earlier in the process, then everything that needs undoing will get
undone as part of ending the request.

-- 
Jens Axboe