Subject: CVE-2024-26947: ARM: 9359/1: flush: check if the folio is reserved for no-mapping addresses

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

ARM: 9359/1: flush: check if the folio is reserved for no-mapping addresses

Since commit a4d5613c4dc6 ("arm: extend pfn_valid to take into account
freed memory map alignment") changes the semantics of pfn_valid() to check
presence of the memory map for a PFN. A valid page for an address which
is reserved but not mapped by the kernel[1], the system crashed during
some uio test with the following memory layout:

 node   0: [mem 0x00000000c0a00000-0x00000000cc8fffff]
 node   0: [mem 0x00000000d0000000-0x00000000da1fffff]
 the uio layout is：0xc0900000, 0x100000

the crash backtrace like:

  Unable to handle kernel paging request at virtual address bff00000
  [...]
  CPU: 1 PID: 465 Comm: startapp.bin Tainted: G           O      5.10.0 #1
  Hardware name: Generic DT based system
  PC is at b15_flush_kern_dcache_area+0x24/0x3c
  LR is at __sync_icache_dcache+0x6c/0x98
  [...]
   (b15_flush_kern_dcache_area) from (__sync_icache_dcache+0x6c/0x98)
   (__sync_icache_dcache) from (set_pte_at+0x28/0x54)
   (set_pte_at) from (remap_pfn_range+0x1a0/0x274)
   (remap_pfn_range) from (uio_mmap+0x184/0x1b8 [uio])
   (uio_mmap [uio]) from (__mmap_region+0x264/0x5f4)
   (__mmap_region) from (__do_mmap_mm+0x3ec/0x440)
   (__do_mmap_mm) from (do_mmap+0x50/0x58)
   (do_mmap) from (vm_mmap_pgoff+0xfc/0x188)
   (vm_mmap_pgoff) from (ksys_mmap_pgoff+0xac/0xc4)
   (ksys_mmap_pgoff) from (ret_fast_syscall+0x0/0x5c)
  Code: e0801001 e2423001 e1c00003 f57ff04f (ee070f3e)
  ---[ end trace 09cf0734c3805d52 ]---
  Kernel panic - not syncing: Fatal exception

So check if PG_reserved was set to solve this issue.

[1]: https://lore.kernel.org/lkml/[email-masked]/

The Linux kernel CVE team has assigned CVE-2024-26947 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.14 with commit a4d5613c4dc6 and fixed in 6.6.24 with commit 0c027c2bad7f
	Issue introduced in 5.14 with commit a4d5613c4dc6 and fixed in 6.7.12 with commit 9f7ddc222cae
	Issue introduced in 5.14 with commit a4d5613c4dc6 and fixed in 6.8.3 with commit fb3a122a9786
	Issue introduced in 5.14 with commit a4d5613c4dc6 and fixed in 6.9 with commit 0c66c6f4e21c
	Issue introduced in 5.4.167 with commit 6026d4032dbb
	Issue introduced in 5.10.87 with commit 65c578935bcc

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26947
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	arch/arm/mm/flush.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/0c027c2bad7f5111c51a358b5d392e1a695dabff
	https://git.kernel.org/stable/c/9f7ddc222cae8254e93d5c169a8ae11a49d912a7
	https://git.kernel.org/stable/c/fb3a122a978626b33de3367ee1762da934c0f512
	https://git.kernel.org/stable/c/0c66c6f4e21cb22220cbd8821c5c73fc157d20dc