CVE-2023-53584

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

ubifs: ubifsreleasepage: Remove ubifsassert(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] ubifswriteend attachpageprivate // set Private _setpagedirtynobuffers // set Dirty unlock(page)

writecachepages[PA] lock(page) clearpagedirtyforio(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): ubifsassertfailed [ubifs]: UBIFS assert failed: 0, in fs/ubifs/file.c:1513 UBIFS warning (ubi0:0 pid 1683): ubifsromode [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: dumpstack+0x13/0x1b ubifsromode+0x54/0x60 [ubifs] ubifsassertfailed+0x4b/0x80 [ubifs] ubifsreleasepage+0x67/0x1d0 [ubifs] trytoreleasepage+0x57/0xe0 invalidateinode_page+0xfb/0x130 _invalidatemappingpages+0xb9/0x280 invalidatemappingpagevec+0x12/0x20 genericfadvise+0x303/0x3c0 ksysfadvise6464+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