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From: Omar Sandoval <osandov@osandov.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-btrfs <linux-btrfs@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH RESEND x3 v9 1/9] iov_iter: add copy_struct_from_iter()
Date: Fri, 18 Jun 2021 17:43:21 -0700	[thread overview]
Message-ID: <YM09qaP3qATwoLTJ@relinquished.localdomain> (raw)
In-Reply-To: <YM0fFnMFSFpUb63U@zeniv-ca.linux.org.uk>

On Fri, Jun 18, 2021 at 10:32:54PM +0000, Al Viro wrote:
> On Fri, Jun 18, 2021 at 03:10:03PM -0700, Omar Sandoval wrote:
> 
> > Or do the same reverting thing that Al did, but with copy_from_iter()
> > instead of copy_from_iter_full() and being careful with the copied count
> > (which I'm not 100% sure I got correct here):
> > 
> > 	size_t copied = copy_from_iter(&encoded, sizeof(encoded), &i);
> > 	if (copied < offsetofend(struct encoded_iov, size))
> > 		return -EFAULT;
> > 	if (encoded.size > PAGE_SIZE)
> > 		return -E2BIG;
> > 	if (encoded.size < ENCODED_IOV_SIZE_VER0)
> > 		return -EINVAL;
> > 	if (encoded.size > sizeof(encoded)) {
> > 		if (copied < sizeof(encoded)
> > 			return -EFAULT;
> > 		if (!iov_iter_check_zeroes(&i, encoded.size - sizeof(encoded))
> > 			return -EINVAL;
> > 	} else if (encoded.size < sizeof(encoded)) {
> > 		// older than what we expect
> > 		if (copied < encoded.size)
> > 			return -EFAULT;
> > 		iov_iter_revert(&i, copied - encoded.size);
> > 		memset((void *)&encoded + encoded.size, 0, sizeof(encoded) - encoded.size);
> > 	}    
> 
> simpler than that, actually -
> 
> 	copied = copy_from_iter(&encoded, sizeof(encoded), &i);
> 	if (unlikely(copied < sizeof(encoded))) {
> 		if (copied < offsetofend(struct encoded_iov, size) ||
> 		    copied < encoded.size)
> 			return iov_iter_count(i) ? -EFAULT : -EINVAL;
> 	}
> 	if (encoded.size > sizeof(encoded)) {
> 		if (!iov_iter_check_zeroes(&i, encoded.size - sizeof(encoded))
> 			return -EINVAL;
> 	} else if (encoded.size < sizeof(encoded)) {
> 		// copied can't be less than encoded.size here - otherwise
> 		// we'd have copied < sizeof(encoded) and the check above
> 		// would've buggered off
> 		iov_iter_revert(&i, copied - encoded.size);
> 		memset((void *)&encoded + encoded.size, 0, sizeof(encoded) - encoded.size);
> 	}
> 
> should do it.

Thanks, Al, I'll send an updated version with this approach next week.

  reply	other threads:[~2021-06-19  0:43 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-17 23:51 [PATCH RESEND x3 v9 0/9] fs: interface for directly reading/writing compressed data Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 1/9] iov_iter: add copy_struct_from_iter() Omar Sandoval
2021-06-18 18:50   ` Linus Torvalds
2021-06-18 19:42     ` Al Viro
2021-06-18 19:49       ` Al Viro
2021-06-18 20:33         ` Omar Sandoval
2021-06-18 20:32       ` Omar Sandoval
2021-06-18 20:58         ` Al Viro
2021-06-18 21:10           ` Linus Torvalds
2021-06-18 21:32             ` Al Viro
2021-06-18 21:40               ` Linus Torvalds
2021-06-18 22:10                 ` Omar Sandoval
2021-06-18 22:32                   ` Al Viro
2021-06-19  0:43                     ` Omar Sandoval [this message]
2021-06-21 18:46                       ` Omar Sandoval
2021-06-21 19:33                         ` Linus Torvalds
2021-06-21 20:46                           ` Omar Sandoval
2021-06-21 20:53                             ` Omar Sandoval
2021-06-21 20:55                             ` Omar Sandoval
2021-06-22 22:06                               ` Dave Chinner
2021-06-23 17:49                                 ` Omar Sandoval
2021-06-23 18:28                                   ` Linus Torvalds
2021-06-23 19:33                                     ` Omar Sandoval
2021-06-23 19:45                                   ` Al Viro
2021-06-23 20:46                                     ` Omar Sandoval
2021-06-23 21:39                                       ` Al Viro
2021-06-23 21:58                                         ` Omar Sandoval
2021-06-23 22:26                                           ` Al Viro
2021-06-24  2:00                                           ` Matthew Wilcox
2021-06-24  6:14                                             ` Omar Sandoval
2021-06-24 17:52                                               ` Linus Torvalds
2021-06-24 18:28                                                 ` Omar Sandoval
2021-06-24 21:07                                                   ` Linus Torvalds
2021-06-24 22:41                                                     ` Martin K. Petersen
2021-06-25  3:38                                                       ` Matthew Wilcox
2021-06-25 16:16                                                         ` Linus Torvalds
2021-06-25 21:07                                                           ` Omar Sandoval
2021-07-07 17:59                                                             ` Omar Sandoval
2021-07-19 15:44                                                               ` Josef Bacik
2021-06-24  6:41                                             ` Christoph Hellwig
2021-06-24  7:50                                               ` Omar Sandoval
2021-06-18 22:14                 ` Al Viro
2021-06-17 23:51 ` [PATCH RESEND x3 v9 2/9] fs: add O_ALLOW_ENCODED open flag Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 3/9] fs: add RWF_ENCODED for reading/writing compressed data Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 4/9] btrfs: don't advance offset for compressed bios in btrfs_csum_one_bio() Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 5/9] btrfs: add ram_bytes and offset to btrfs_ordered_extent Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 6/9] btrfs: support different disk extent size for delalloc Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 7/9] btrfs: optionally extend i_size in cow_file_range_inline() Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 8/9] btrfs: implement RWF_ENCODED reads Omar Sandoval
2021-06-17 23:51 ` [PATCH RESEND x3 v9 9/9] btrfs: implement RWF_ENCODED writes Omar Sandoval

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