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Message-ID: <CAGWkznG4hiQGb4uYCAiLTgvJ_tZt5s-2h+X_1T3uOmm+U04fTg@mail.gmail.com>
Date: Tue, 20 Aug 2019 20:45:41 +0800
From: Zhaoyang Huang <huangzhaoyang@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Zhaoyang Huang <zhaoyang.huang@...soc.com>,
Russell King <linux@...linux.org.uk>,
Mike Rapoport <rppt@...ux.ibm.com>,
Rob Herring <robh@...nel.org>,
Florian Fainelli <f.fainelli@...il.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Doug Berger <opendmb@...il.com>,
LKML <linux-kernel@...r.kernel.org>, chunyan.zhang@...soc.com
Subject: [Resend PATCH v3] arch : arm : add a criteria for pfn_valid
From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
pfn_valid can be wrong when parsing a invalid pfn whose phys address
exceeds BITS_PER_LONG as the MSB will be trimed when shifted.
The issue originally arise from bellowing call stack, which corresponding to
an access of the /proc/kpageflags from userspace with a invalid pfn parameter
and leads to kernel panic.
[46886.723249] c7 [<c031ff98>] (stable_page_flags) from [<c03203f8>]
[46886.723264] c7 [<c0320368>] (kpageflags_read) from [<c0312030>]
[46886.723280] c7 [<c0311fb0>] (proc_reg_read) from [<c02a6e6c>]
[46886.723290] c7 [<c02a6e24>] (__vfs_read) from [<c02a7018>]
[46886.723301] c7 [<c02a6f74>] (vfs_read) from [<c02a778c>]
[46886.723315] c7 [<c02a770c>] (SyS_pread64) from [<c0108620>]
(ret_fast_syscall+0x0/0x28)
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
Reviewed-by: Mike Rapoport <rppt@...ux.ibm.com>
---
v2: use __pfn_to_phys/__phys_to_pfn instead of max_pfn as the criteria
v3: update commit message to describe the defection's context
add Mike Rapoport as reviewer
---
arch/arm/mm/init.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index c2daabb..cc769fa 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -177,6 +177,11 @@ static void __init zone_sizes_init(unsigned long
min, unsigned long max_low,
#ifdef CONFIG_HAVE_ARCH_PFN_VALID
int pfn_valid(unsigned long pfn)
{
+ phys_addr_t addr = __pfn_to_phys(pfn);
+
+ if (__phys_to_pfn(addr) != pfn)
+ return 0;
+
return memblock_is_map_memory(__pfn_to_phys(pfn));
}
EXPORT_SYMBOL(pfn_valid);
--
1.9.1
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