nilfs2: reject invalid block index in GC ioctl

Overview

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.

Affected

• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < 898404cdf882d7b54f1132f75570984ca3214796
• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < ba8a8b563a28d358c45c62a306d421434a058648
• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < 3bd064ccc70b85f9a3d53aece29dc8473be5a226
• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < a5e776e2937581d67ec5b9b4d27b0f70d7baa6b1
• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < 68aa9ab6f8f2895713aa6ddf781463ed8ea5ba44
• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < e447f7edb99bd00cec63d6f3049e2e5074946f71
• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < ec6ddf271dfa4c7e3147bc2c8b2bad4315f316a1
• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < fbcfb75c20d71a5b542ad4ac3b79d10b997c8152
• Linux >= 7942b919f7321f95a777d396ff7894a7a83dc9b0 < a1735eae55448bc79c2da6593455791e886f6ed8
• Linux 2.6.30

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.