md/md-bitmap: fix wrong bitmap_limit for clustermd when write sb

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: md/md-bitmap: fix wrong bitmap_limit for clustermd when write sb In clustermd, separate write-intent-bitmaps are used for each cluster node: 0 4k 8k 12k ------------------------------------------------------------------- | idle | md super | bm super [0] + bits | | bm bits[0, contd] | bm super[1] + bits | bm bits[1, contd] | | bm super[2] + bits | bm bits [2, contd] | bm super[3] + bits | | bm bits [3, contd] | | | So in node 1, pg_index in __write_sb_page() could equal to bitmap->storage.file_pages. Then bitmap_limit will be calculated to 0. md_super_write() will be called with 0 size. That means the first 4k sb area of node 1 will never be updated through filemap_write_page(). This bug causes hang of mdadm/clustermd_tests/01r1_Grow_resize. Here use (pg_index % bitmap->storage.file_pages) to make calculation of bitmap_limit correct.

References

• https://git.kernel.org/stable/c/60196f92bbc7901eb5cfa5d456651b87ea50a4a3
• https://git.kernel.org/stable/c/bc3a9788961631359527763d7e1fcf26554c7cb1
• https://git.kernel.org/stable/c/6130825f34d41718c98a9b1504a79a23e379701e