linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: avoid wrong decrypted data from disk

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Date:   Thu, 30 Aug 2018 13:19:42 +0530
From:   Sahitya Tummala <stummala@...eaurora.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: avoid wrong decrypted data from disk

On Thu, Aug 30, 2018 at 11:59:03AM +0530, Sahitya Tummala wrote:
> On Mon, Aug 27, 2018 at 03:52:26PM -0700, Jaegeuk Kim wrote:
> > 1. Create a file in an encrypted directory
> > 2. Do GC & drop caches
> > 3. Read stale data before its bio for metapage was not issued yet
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> >  fs/f2fs/data.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 382c1ef9a9e4..c3557fd4a0bd 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -1550,6 +1550,13 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
> >  			bio = NULL;
> >  		}
> >  		if (bio == NULL) {
> > +			/*
> > +			 * If the page is under writeback, we need to wait for
> > +			 * its completion to see the correct decrypted data.
> > +			 */
> > +			if (unlikely(f2fs_encrypted_file(inode)))
> > +				f2fs_wait_on_block_writeback(F2FS_I_SB(inode), block_nr);
> > +
> 
> I am not sure if this really helps the case.
> 
> When the data is being moved by GC, the writeback is set on the encrypted page
> which belongs to meta mapping. But before that writeback could complete, the read
> will happen on the original file where it's corresponding page will not have any
> writeback set, right?

Never mind, got it. Tested with your latest v3 patch and it is fixing the
problem. Thanks.

> 
> >  			bio = f2fs_grab_read_bio(inode, block_nr, nr_pages,
> >  					is_readahead ? REQ_RAHEAD : 0);
> >  			if (IS_ERR(bio)) {
> > -- 
> > 2.17.0.441.gb46fe60e1d-goog
> > 
> > 
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> 
> -- 
> --
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> 
> ------------------------------------------------------------------------------
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Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.