CVE-2023-53584

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

ubifs: ubifs_releasepage: Remove ubifs_assert(0) to valid this process

There are two states for ubifs writing pages:

1. Dirty, Private
2. Not Dirty, Not Private

The normal process cannot go to ubifs_releasepage() which means there exists pages being private but not dirty. Reproducer[1] shows that it could occur (which maybe related to [2]) with following process:

 PA                     PB                    PC

lock(page)[PA] ubifs_write_end attach_page_private // set Private __set_page_dirty_nobuffers // set Dirty unlock(page)

write_cache_pages[PA] lock(page) clear_page_dirty_for_io(page) // clear Dirty ubifs_writepage

                    do_truncation[PB]
		  truncate_setsize
		    i_size_write(inode, newsize) // newsize = 0

i_size = i_size_read(inode)	// i_size = 0
end_index = i_size >> PAGE_SHIFT
if (page->index > end_index)
  goto out // jump

out: unlock(page) // Private, Not Dirty

					generic_fadvise[PC]
					  lock(page)
					  invalidate_inode_page
					    try_to_release_page
					      ubifs_releasepage
					        ubifs_assert(c, 0)
	                                        // bad assertion!
					  unlock(page)
		  truncate_pagecache[PB]

Then we may get following assertion failed: UBIFS error (ubi0:0 pid 1683): ubifs_assert_failed [ubifs]: UBIFS assert failed: 0, in fs/ubifs/file.c:1513 UBIFS warning (ubi0:0 pid 1683): ubifs_ro_mode [ubifs]: switched to read-only mode, error -22 CPU: 2 PID: 1683 Comm: aa Not tainted 5.16.0-rc5-00184-g0bca5994cacc-dirty #308 Call Trace: dump_stack+0x13/0x1b ubifs_ro_mode+0x54/0x60 [ubifs] ubifs_assert_failed+0x4b/0x80 [ubifs] ubifs_releasepage+0x67/0x1d0 [ubifs] try_to_release_page+0x57/0xe0 invalidate_inode_page+0xfb/0x130 __invalidate_mapping_pages+0xb9/0x280 invalidate_mapping_pagevec+0x12/0x20 generic_fadvise+0x303/0x3c0 ksys_fadvise64_64+0x4c/0xb0

[1] https://bugzilla.kernel.org/show_bug.cgi?id=215373 [2] https://linux-mtd.infradead.narkive.com/NQoBeT1u/patch-rfc-ubifs-fix-assert-failed-in-ubifs-set-page-dirty

Affected Software

References

• https://git.kernel.org/stable/c/66f4742e93523ab2f062d9d9828b3e590bc61536
• https://git.kernel.org/stable/c/7750be5d3e18500b454714677463b500a0b8b0d8
• https://git.kernel.org/stable/c/bd188ff1c8a1935c93a1e3cacf3be62667fdf762