Patch "ARM: 9359/1: flush: check if the folio is reserved for no-mapping addresses" has been added to the 6.6-stable tree

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This is a note to let you know that I've just added the patch titled

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

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-9359-1-flush-check-if-the-folio-is-reserved-for-.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit bbde1cf0420176768bd274e039fba471f2454d55
Author: Yongqiang Liu <liuyongqiang13@xxxxxxxxxx>
Date:   Thu Mar 7 13:05:09 2024 +0100

    ARM: 9359/1: flush: check if the folio is reserved for no-mapping addresses
    
    [ Upstream commit 0c66c6f4e21cb22220cbd8821c5c73fc157d20dc ]
    
    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@xxxxxxxxxxxxx/
    
    Fixes: a4d5613c4dc6 ("arm: extend pfn_valid to take into account freed memory map alignment")
    Suggested-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
    Signed-off-by: Yongqiang Liu <liuyongqiang13@xxxxxxxxxx>
    Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index d19d140a10c7d..0749cf8a66371 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -296,6 +296,9 @@ void __sync_icache_dcache(pte_t pteval)
 		return;
 
 	folio = page_folio(pfn_to_page(pfn));
+	if (folio_test_reserved(folio))
+		return;
+
 	if (cache_is_vipt_aliasing())
 		mapping = folio_flush_mapping(folio);
 	else




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