[PATCH 4.19 55/79] ARM: 8901/1: add a criteria for pfn_valid of arm

Greg Kroah-Hartman
2019-09-19T22:14:05Z

From: zhaoyang <huangzhaoyang@gmail.com>

[ Upstream commit 5b3efa4f1479c91cb8361acef55f9c6662feba57 ]

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@unisoc.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 66b1568b95e05..e1d330a269212 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -196,6 +196,11 @@ 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);
--
2.20.1