From b58b1b883b9b702e25204dbe2b221eecc8ecd159 Mon Sep 17 00:00:00 2001 From: Brian Foster <bfoster@redhat.com> Date: Thu, 15 Feb 2024 12:16:05 -0500 Subject: [PATCH] bcachefs: fix iov_iter count underflow on sub-block dio read bch2_direct_IO_read() checks the request offset and size for sector alignment and then falls through to a couple calculations to shrink the size of the request based on the inode size. The problem is that these checks round up to the fs block size, which runs the risk of underflowing iter->count if the block size happens to be large enough. This is triggered by fstest generic/361 with a 4k block size, which subsequently leads to a crash. To avoid this crash, check that the shorten length doesn't exceed the overall length of the iter. Fixes: Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Su Yue <glass.su@suse.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev> --- fs/bcachefs/fs-io-direct.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/bcachefs/fs-io-direct.c b/fs/bcachefs/fs-io-direct.c index e3b219e19e100..33cb6da3a5ad2 100644 --- a/fs/bcachefs/fs-io-direct.c +++ b/fs/bcachefs/fs-io-direct.c @@ -88,6 +88,8 @@ static int bch2_direct_IO_read(struct kiocb *req, struct iov_iter *iter) return ret; shorten = iov_iter_count(iter) - round_up(ret, block_bytes(c)); + if (shorten >= iter->count) + shorten = 0; iter->count -= shorten; bio = bio_alloc_bioset(NULL, -- GitLab