Message ID | 20181107063127.3902-6-david@fromorbit.com (mailing list archive) |
---|---|
State | Superseded |
Headers | show |
Series | xfs: Block size > PAGE_SIZE support | expand |
On Wed, Nov 07, 2018 at 05:31:16PM +1100, Dave Chinner wrote: > From: Dave Chinner <dchinner@redhat.com> > > If we are soing sub-block dio that extends EOF, we need to zero > the unused tail of the block to initialise the data in it it. If we > do not zero the tail of the block, then an immediate mmap read of > the EOF block will expose stale data beyond EOF to userspace. Found > with fsx running sub-block DIO sizes vs MAPREAD/MAPWRITE operations. > > Fix this by detecting if the end of the DIO write is beyond EOF > and zeroing the tail if necessary. > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > --- > fs/iomap.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/fs/iomap.c b/fs/iomap.c > index 64ce240217a1..16d16596b00f 100644 > --- a/fs/iomap.c > +++ b/fs/iomap.c > @@ -1676,7 +1676,14 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, > dio->submit.cookie = submit_bio(bio); > } while (nr_pages); > > - if (need_zeroout) { > + /* > + * We need to zeroout the tail of a sub-block write if th extent type s/th/the/ Otherwise this looks fine to me: Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/iomap.c b/fs/iomap.c index 64ce240217a1..16d16596b00f 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -1676,7 +1676,14 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, dio->submit.cookie = submit_bio(bio); } while (nr_pages); - if (need_zeroout) { + /* + * We need to zeroout the tail of a sub-block write if th extent type + * requires zeroing or the write extends beyond EOF. If we don't zero + * the block tail in the latter case, we can expose stale data via mmap + * reads of the EOF block. + */ + if (need_zeroout || + ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) { /* zero out from the end of the write to the end of the block */ pad = pos & (fs_block_size - 1); if (pad)