linux-kernel - [PATCH] arm: flush: don't abuse pfn_valid() to check if pfn is in RAM

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Date: Wed, 31 Jan 2024 20:59:07 +0800
From: Yongqiang Liu <liuyongqiang13@...wei.com>
To: <linux-arm-kernel@...ts.infradead.org>
CC: <yanaijie@...wei.com>, <zhangxiaoxu5@...wei.com>,
	<wangkefeng.wang@...wei.com>, <sunnanyong@...wei.com>,
	<linux@...linux.org.uk>, <rppt@...ux.ibm.com>,
	<linux-kernel@...r.kernel.org>, <keescook@...omium.org>, <arnd@...db.de>,
	<m.szyprowski@...sung.com>, <willy@...radead.org>,
	<liuyongqiang13@...wei.com>
Subject: [PATCH] arm: flush: don't abuse pfn_valid() to check if pfn is in RAM

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. __sync_icache_dcache() should use
memblock_is_map_memory() instead of pfn_valid() to check if a PFN is in
RAM or not.In Some uio case we will get a crash on a system 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

Fixes: a4d5613c4dc6 ("arm: extend pfn_valid to take into account freed memory map alignment")
Signed-off-by: Yongqiang Liu <liuyongqiang13@...wei.com>
---
 arch/arm/mm/flush.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index d19d140a10c7..11ec6c5ff5fc 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -15,6 +15,7 @@
 #include <asm/smp_plat.h>
 #include <asm/tlbflush.h>
 #include <linux/hugetlb.h>
+#include <linux/memblock.h>
 
 #include "mm.h"
 
@@ -292,7 +293,7 @@ void __sync_icache_dcache(pte_t pteval)
 		/* only flush non-aliasing VIPT caches for exec mappings */
 		return;
 	pfn = pte_pfn(pteval);
-	if (!pfn_valid(pfn))
+	if (!memblock_is_map_memory(PFN_PHYS(pfn)))
 		return;
 
 	folio = page_folio(pfn_to_page(pfn));
-- 
2.25.1