Re: [PATCH] staging/android: refactor SYNC_IOC_FILE_INFO

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi Maarten,

2016-03-01 Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>:

> Op 29-02-16 om 23:08 schreef Gustavo Padovan:
> > Hi Maarten,
> >
> > 2016-02-29 Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>:
> >
> >> Op 26-02-16 om 22:00 schreef Gustavo Padovan:
> >>> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> >>>
> >>> 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.
> > Yes, I agree.
> >
> >>> 		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@xxxxxxxxxxxxxxx>
> >>> ---
> >>>  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);
> > I think of len being useful if we decide to extend struct sync_fence_info in
> > the future, so we may use len to help discover the size of each
> > sync_fence_info. What do you think?
> >
> I don't think you could extend it arbitrarily, you could make userspace pass a flag to indicate the struct is extended, so kernel space can choose
> whether to use the bigger size struct or not.
> 
> something like sync_file_info.flags = FENCE_INFO_V2; -- kernel can reject with -EINVAL if unsupported, or fill in a v2 struct.

Fair enough, I'll just remove len then.

	Gustavo
_______________________________________________
devel mailing list
devel@xxxxxxxxxxxxxxxxxxxxxx
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel



[Index of Archives]     [Linux Driver Backports]     [DMA Engine]     [Linux GPIO]     [Linux SPI]     [Video for Linux]     [Linux USB Devel]     [Linux Coverity]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [Yosemite Backpacking]
  Powered by Linux