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H A D | blk-map.c | 0f1bae07 Sun Jan 21 14:26:34 CST 2024 Christian A. Ehrhardt <lk@c--e.de> block: Fix WARNING in _copy_from_iter
[ Upstream commit 13f3956eb5681a4045a8dfdef48df5dc4d9f58a6 ]
Syzkaller reports a warning in _copy_from_iter because an iov_iter is supposedly used in the wrong direction. The reason is that syzcaller managed to generate a request with a transfer direction of SG_DXFER_TO_FROM_DEV. This instructs the kernel to copy user buffers into the kernel, read into the copied buffers and then copy the data back to user space.
Thus the iovec is used in both directions.
Detect this situation in the block layer and construct a new iterator with the correct direction for the copy-in.
Reported-by: syzbot+a532b03fdfee2c137666@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/0000000000009b92c10604d7a5e9@google.com/t/ Reported-by: syzbot+63dec323ac56c28e644f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/0000000000003faaa105f6e7c658@google.com/T/ Signed-off-by: Christian A. Ehrhardt <lk@c--e.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20240121202634.275068-1-lk@c--e.de Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>
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