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Message-ID: <56D400CD.6070804@linux.intel.com>
Date: Mon, 29 Feb 2016 09:26:53 +0100
From: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
To: Gustavo Padovan <gustavo@...ovan.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
dri-devel@...ts.freedesktop.org,
Daniel Stone <daniels@...labora.com>,
Arve Hjønnevåg <arve@...roid.com>,
Riley Andrews <riandrews@...roid.com>,
Daniel Vetter <daniel.vetter@...ll.ch>,
Rob Clark <robdclark@...il.com>,
Greg Hackmann <ghackmann@...gle.com>,
John Harrison <John.C.Harrison@...el.com>,
Gustavo Padovan <gustavo.padovan@...labora.co.uk>
Subject: Re: [PATCH] staging/android: refactor SYNC_IOC_FILE_INFO
Op 26-02-16 om 22:00 schreef Gustavo Padovan:
> From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
>
> Change SYNC_IOC_FILE_INFO behaviour to avoid future API breaks and
> optimize buffer allocation. In the new approach the ioctl needs to be called
> twice to retrieve the array of fence_infos pointed by info->sync_fence_info.
>
> The first call should pass num_fences = 0, the kernel will then fill
> info->num_fences. Userspace receives back the number of fences and
> allocates a buffer size num_fences * sizeof(struct sync_fence_info) on
> info->sync_fence_info.
>
> It then call the ioctl again passing num_fences received in info->num_fences.
> The kernel checks if info->num_fences > 0 and if yes it fill
> info->sync_fence_info with an array containing all fence_infos.
>
> info->len now represents the length of the buffer sync_fence_info points
> to. Also, info->sync_fence_info was converted to __u64 pointer.
>
> An example userspace code would be:
>
> struct sync_file_info *info;
> int err, size, num_fences;
>
> info = malloc(sizeof(*info));
>
> memset(info, 0, sizeof(*info));
>
> err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> num_fences = info->num_fences;
>
> if (num_fences) {
> memset(info, 0, sizeof(*info));
Would this memset still be needed if we didn't check for nulls in info->status and info->name ?
Seems to me that it could be skipped in that case.
> size = sizeof(struct sync_fence_info) * num_fences;
> info->len = size;
> info->num_fences = num_fences;
> info->sync_fence_info = (uint64_t) calloc(num_fences,
> sizeof(struct sync_fence_info));
>
> err = ioctl(fd, SYNC_IOC_FILE_INFO, info);
> }
>
> v2: fix fence_info memory leak
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> ---
> drivers/staging/android/sync.c | 52 +++++++++++++++++++++++++++++--------
> drivers/staging/android/uapi/sync.h | 9 +++----
> 2 files changed, 45 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c
> index dc5f382..2379f23 100644
> --- a/drivers/staging/android/sync.c
> +++ b/drivers/staging/android/sync.c
> @@ -502,21 +502,22 @@ static int sync_fill_fence_info(struct fence *fence, void *data, int size)
> static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> unsigned long arg)
> {
> - struct sync_file_info *info;
> + struct sync_file_info in, *info;
> + struct sync_fence_info *fence_info = NULL;
> __u32 size;
> __u32 len = 0;
= 0 unneeded.
> int ret, i;
>
> - if (copy_from_user(&size, (void __user *)arg, sizeof(size)))
> + if (copy_from_user(&in, (void __user *)arg, sizeof(*info)))
> return -EFAULT;
>
> - if (size < sizeof(struct sync_file_info))
> - return -EINVAL;
> + if (in.status || strcmp(in.name, "\0"))
> + return -EFAULT;
These members always get written by the fence ioctl, I'm not sure it adds value to have them explicitly zero'd out by userspace.
> - if (size > 4096)
> - size = 4096;
> + if (in.num_fences && !in.sync_fence_info)
> + return -EFAULT;
This check is unneeded, it will happen in the copy_to_user call anyway.
> - info = kzalloc(size, GFP_KERNEL);
> + info = kzalloc(sizeof(*info), GFP_KERNEL);
> if (!info)
> return -ENOMEM;
>
> @@ -525,14 +526,33 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> if (info->status >= 0)
> info->status = !info->status;
>
> - info->num_fences = sync_file->num_fences;
> + /*
> + * Passing num_fences = 0 means that userspace want to know how
> + * many fences are in the sync_file to be able to allocate a buffer to
> + * fit all sync_fence_infos and call the ioctl again with the buffer
> + * assigned to info->sync_fence_info. The second call pass the
> + * num_fences value received in the first call.
> + */
> + if (!in.num_fences)
> + goto no_fences;
> +
> + size = sync_file->num_fences * sizeof(*fence_info);
> + if (in.len != size) {
> + ret = -EFAULT;
> + goto out;
> + }
Maybe check for in.len < size, and set set to size?
> - len = sizeof(struct sync_file_info);
> + fence_info = kzalloc(size, GFP_KERNEL);
> + if (!fence_info) {
> + ret = -ENOMEM;
> + goto out;
> + }
>
> for (i = 0; i < sync_file->num_fences; ++i) {
> struct fence *fence = sync_file->cbs[i].fence;
>
> - ret = sync_fill_fence_info(fence, (u8 *)info + len, size - len);
> + ret = sync_fill_fence_info(fence, (u8 *)fence_info + len,
> + size - len);
>
> if (ret < 0)
> goto out;
> @@ -540,14 +560,24 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> len += ret;
> }
>
> + if (copy_to_user((void __user *)in.sync_fence_info, fence_info, size)) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> info->len = len;
> + info->sync_fence_info = (__u64) in.sync_fence_info;
> +
> +no_fences:
> + info->num_fences = sync_file->num_fences;
>
> - if (copy_to_user((void __user *)arg, info, len))
> + if (copy_to_user((void __user *)arg, info, sizeof(*info)))
> ret = -EFAULT;
> else
> ret = 0;
>
> out:
> + kfree(fence_info);
> kfree(info);
>
> return ret;
> diff --git a/drivers/staging/android/uapi/sync.h b/drivers/staging/android/uapi/sync.h
> index f0b41ce..9aad623 100644
> --- a/drivers/staging/android/uapi/sync.h
> +++ b/drivers/staging/android/uapi/sync.h
> @@ -42,21 +42,20 @@ struct sync_fence_info {
>
> /**
> * struct sync_file_info - data returned from fence info ioctl
> - * @len: ioctl caller writes the size of the buffer its passing in.
> - * ioctl returns length of sync_file_info returned to
> - * userspace including pt_info.
> * @name: name of fence
> * @status: status of fence. 1: signaled 0:active <0:error
> * @num_fences number of fences in the sync_file
> + * @len: ioctl caller writes the size of the buffer its passing in.
> + * ioctl returns length of all fence_infos summed.
> * @sync_fence_info: array of sync_fence_info for every fence in the sync_file
> */
> struct sync_file_info {
> - __u32 len;
> char name[32];
> __s32 status;
> __u32 num_fences;
> + __u32 len;
>
> - __u8 sync_fence_info[0];
> + __u64 sync_fence_info;
> };
>
> #define SYNC_IOC_MAGIC '>'
Not sure if len adds anything here, userspace knows to allocate num_fences * sizeof(struct sync_fence_info);
It could probably be removed since num_fences would do the same.
~Maarten
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