Commit 893e5e9b authored by Gao Xiang's avatar Gao Xiang
Browse files

erofs: fix uninitialized page cache reported by KMSAN 

syzbot reports a KMSAN reproducer [1] which generates a crafted
filesystem image and causes IMA to read uninitialized page cache.

Later, (rq->outputsize > rq->inputsize) will be formally supported
after either large uncompressed pclusters (> block size) or big
lclusters are landed.  However, currently there is no way to generate
such filesystems by using mkfs.erofs.

Thus, let's mark this condition as unsupported for now.

[1] https://lore.kernel.org/r/0000000000002be12a0611ca7ff8@google.com



Reported-and-tested-by: default avatar <syzbot+7bc44a489f0ef0670bd5@syzkaller.appspotmail.com>
Fixes: 1ca01520 ("erofs: refine z_erofs_transform_plain() for sub-page block support")
Reviewed-by: default avatarSandeep Dhavale <dhavale@google.com>
Reviewed-by: default avatarYue Hu <huyue2@coolpad.com>
Reviewed-by: default avatarChao Yu <chao@kernel.org>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240304035339.425857-1-hsiangkao@linux.alibaba.com
parent 90d35da6

fs/erofs/decompressor.c

+2 −1
Original line number Diff line number Diff line
@@ -323,7 +323,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq, 
	unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;

	u8 *kin;



	DBG_BUGON(rq->outputsize > rq->inputsize);

	if (rq->outputsize > rq->inputsize)

		return -EOPNOTSUPP;

	if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {

		cur = bs - (rq->pageofs_out & (bs - 1));

		pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;