[SRU][J][PATCH v2 1/1] ARM: 9359/1: flush: check if the folio is reserved for no-mapping addresses

[Koichiro Den]

From: Yongqiang Liu <liuyongqiang13 at huawei.com>

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/Zbtdue57RO0QScJM@linux.ibm.com/

Fixes: a4d5613c4dc6 ("arm: extend pfn_valid to take into account freed memory map alignment")
Suggested-by: Mike Rapoport <rppt at linux.ibm.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13 at huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel at armlinux.org.uk>
(backported from commit 0c66c6f4e21cb22220cbd8821c5c73fc157d20dc)
[koichiroden: folio_test_reserved replaced by PageReserved due to
 missing commit 8b5989f33337 ("arm: implement the new page table range
 API"). folio conversion is not backported in general, so notice that
 even d389a4a81155 ("mm: Add folio flag manipulation functions") does
 not exist in Xenial]
CVE-2024-26947
Signed-off-by: Koichiro Den <koichiro.den at canonical.com>
---
 arch/arm/mm/flush.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 7ff9feea13a6..b19ecc307ad4 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -280,6 +280,8 @@ void __sync_icache_dcache(pte_t pteval)
 		return;
 
 	page = pfn_to_page(pfn);
+	if (PageReserved(page))
+		return;
 	if (cache_is_vipt_aliasing())
 		mapping = page_mapping_file(page);
 	else
-- 
2.43.0