From: Stefan Roesch <[email protected]>
To: Al Viro <[email protected]>
Cc: <[email protected]>, <[email protected]>,
<[email protected]>, <[email protected]>,
<[email protected]>
Subject: Re: [PATCH v10 4/5] io_uring: add fsetxattr and setxattr support
Date: Thu, 30 Dec 2021 12:18:39 -0800 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 12/29/21 6:17 PM, Al Viro wrote:
> On Wed, Dec 29, 2021 at 12:30:01PM -0800, Stefan Roesch wrote:
>
>> +static int __io_setxattr_prep(struct io_kiocb *req,
>> + const struct io_uring_sqe *sqe)
>> +{
>> + struct io_xattr *ix = &req->xattr;
>> + const char __user *name;
>> + int ret;
>> +
>> + if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
>> + return -EINVAL;
>> + if (unlikely(sqe->ioprio))
>> + return -EINVAL;
>> + if (unlikely(req->flags & REQ_F_FIXED_FILE))
>> + return -EBADF;
>> +
>> + ix->filename = NULL;
>> + name = u64_to_user_ptr(READ_ONCE(sqe->addr));
>> + ix->ctx.value = u64_to_user_ptr(READ_ONCE(sqe->addr2));
>> + ix->ctx.kvalue = NULL;
>> + ix->ctx.size = READ_ONCE(sqe->len);
>> + ix->ctx.flags = READ_ONCE(sqe->xattr_flags);
>> +
>> + ix->ctx.kname = kmalloc(sizeof(*ix->ctx.kname), GFP_KERNEL);
>> + if (!ix->ctx.kname)
>> + return -ENOMEM;
>> +
>> + ret = setxattr_copy(name, &ix->ctx);
>> + if (ret) {
>> + kfree(ix->ctx.kname);
>> + return ret;
>> + }
>> +
>> + req->flags |= REQ_F_NEED_CLEANUP;
>> + return 0;
>> +}
>
> OK, so you
> * allocate a buffer for xattr name
> * have setxattr_copy() copy the name in *and* memdup the contents
> * on failure, you have the buffer for xattr name freed and return
> an error. memdup'ed stuff is left for cleanup, presumably.
>
>> +static int io_setxattr_prep(struct io_kiocb *req,
>> + const struct io_uring_sqe *sqe)
>> +{
>> + struct io_xattr *ix = &req->xattr;
>> + const char __user *path;
>> + int ret;
>> +
>> + ret = __io_setxattr_prep(req, sqe);
>> + if (ret)
>> + return ret;
>> +
>> + path = u64_to_user_ptr(READ_ONCE(sqe->addr3));
>> +
>> + ix->filename = getname_flags(path, LOOKUP_FOLLOW, NULL);
>> + if (IS_ERR(ix->filename)) {
>> + ret = PTR_ERR(ix->filename);
>> + ix->filename = NULL;
>> + }
>> +
>> + return ret;
>> +}
>
> ... and here you use it and bring the pathname in. Should the latter
> step fail, you restore ->filename to NULL and return an error.
>
> Could you explain what kind of magic could allow the caller to tell
> whether ix->ctx.kname needs to be freed on error? I don't see any way
> that could possibly work...
At the end of the function __io_setxattr_prep() we set the flag REQ_F_NEED_CLEANUP.
If the processing fails for some reason, the cleanup code in io_clean_op() gets called
and the data structures get de-allocated.
In case the request is processed successfully, the memory gets de-allocated in io_setxattr()
and io_fsetxattr() with the helper function __io_setxattr_finish(). The helper function clears
the flag REQ_F_NEED_CLEANUP, so clean up is not necessary.
This is the general pattern of cleanup in io-uring.
I can certainly add a cleanup function, that is called in all 3 cases:
- io_setxattr,
- io_fsetxattr
- io_clean_op
next prev parent reply other threads:[~2021-12-30 20:18 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-29 20:29 [PATCH v10 0/5] io_uring: add xattr support Stefan Roesch
2021-12-29 20:29 ` [PATCH v10 1/5] fs: split off do_user_path_at_empty from user_path_at_empty() Stefan Roesch
2021-12-30 0:49 ` Al Viro
2021-12-30 19:57 ` Stefan Roesch
2021-12-29 20:29 ` [PATCH v10 2/5] fs: split off setxattr_copy and do_setxattr function from setxattr Stefan Roesch
2021-12-30 1:15 ` Al Viro
2021-12-30 9:41 ` Christian Brauner
2021-12-30 19:57 ` Stefan Roesch
2021-12-29 20:30 ` [PATCH v10 3/5] fs: split off do_getxattr from getxattr Stefan Roesch
2021-12-29 20:30 ` [PATCH v10 4/5] io_uring: add fsetxattr and setxattr support Stefan Roesch
2021-12-30 1:58 ` Al Viro
2021-12-30 2:17 ` Al Viro
2021-12-30 2:19 ` Al Viro
2021-12-30 3:04 ` Al Viro
2021-12-30 10:12 ` Christian Brauner
2021-12-30 16:16 ` Al Viro
2021-12-30 18:01 ` Christian Brauner
2021-12-30 19:09 ` Jens Axboe
2021-12-30 22:24 ` Al Viro
2021-12-30 22:46 ` Jens Axboe
2021-12-30 23:02 ` Al Viro
2021-12-30 20:18 ` Stefan Roesch [this message]
2021-12-29 20:30 ` [PATCH v10 5/5] io_uring: add fgetxattr and getxattr support Stefan Roesch
2021-12-30 1:41 ` Al Viro
2021-12-30 1:46 ` Al Viro
2021-12-30 20:01 ` Stefan Roesch
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