CVE-2026-80807

In the Linux kernel, the following vulnerability has been resolved:

nilfs2: reject invalid block index in GC ioctl

Syzbot reported list corruption caused by a double list add tail() call on bh->b assoc buffers within nilfs lookup dirty data buffers().

Analysis revealed that the root cause was the insertion of a page/folio with a page index of ULONG MAX into the page cache via the GC ioctl. filemap get folios tag(), called by nilfs lookup dirty data buffers(), repeatedly detects a dirty folio with a page index of ULONG MAX due to index wrap-around, leading to duplicate processing of dirty buffers.

As a preparatory step, the GC ioctl loads the page/folio of the block to be moved during GC and inserts it into the page cache based on information in the nilfs vdesc structure passed as an argument. Normally, this does not cause issues because the user-space GC library configures the nilfs vdesc structure properly. However, since there is no range check on the parameters determining the page index, a request with artificially crafted parameters -- such as those generated by Syzbot -- can result in a page/folio being inserted with a page index of ULONG MAX, triggering the above problem.

This resolves the issue by checking the ranges of 'vd offset' and 'vd vblocknr' in the nilfs vdesc structure that determine the page index, thereby preventing the invalid page/folio insertions.