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authorDave Chinner <dchinner@redhat.com>2018-11-19 13:31:10 -0800
committerDarrick J. Wong <darrick.wong@oracle.com>2018-11-21 10:10:53 -0800
commitb450672fb66b4a991a5b55ee24209ac7ae7690ce (patch)
treedcee5c6d6b1f32680c4b3a25741247dc1d6bcfe4
parent0929d8580071c6a1cec1a7916a8f674c243ceee1 (diff)
downloadlinux-b450672fb66b4a991a5b55ee24209ac7ae7690ce.tar.bz2
iomap: sub-block dio needs to zeroout beyond EOF
If we are doing 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> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
-rw-r--r--fs/iomap.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/iomap.c b/fs/iomap.c
index 72f3864a2e6b..77c214194edf 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -1677,7 +1677,14 @@ 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 the 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)