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From: Yigal Korman <yigal@plexistor.com>
To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	x86@kernel.org, linux-kernel@vger.kernel.org
Cc: linux-nvdimm@lists.01.org
Subject: [PATCH] x86/mm: only allow memmap=XX!YY over existing RAM
Date: Mon, 20 Jun 2016 10:33:59 +0300	[thread overview]
Message-ID: <1466408039-7497-1-git-send-email-yigal@plexistor.com> (raw)

Before this patch, passing a range that is beyond the physical memory
range will succeed, the user will see a /dev/pmem0 and will be able to
access it. Reads will always return 0 and writes will be silently
ignored.

I've gotten more than one bug report about mkfs.{xfs,ext4} or nvml
failing that were eventually tracked down to be wrong values passed to
memmap.

This patch prevents the above issue by instead of adding a new memory
range, only update a RAM memory range with the PRAM type. This way,
passing the wrong memmap will either not give you a pmem at all or give
you a smaller one that actually has RAM behind it.

And if someone still needs to fake a pmem that doesn't have RAM behind
it, they can simply do memmap=XX@YY,XX!YY.

Signed-off-by: Yigal Korman <yigal@plexistor.com>
---
 arch/x86/kernel/e820.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 621b501..4bd4207 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -878,7 +878,7 @@ static int __init parse_memmap_one(char *p)
 		e820_add_region(start_at, mem_size, E820_RESERVED);
 	} else if (*p == '!') {
 		start_at = memparse(p+1, &p);
-		e820_add_region(start_at, mem_size, E820_PRAM);
+		e820_update_range(start_at, mem_size, E820_RAM, E820_PRAM);
 	} else
 		e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
 
-- 
1.9.3

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Linux-nvdimm@lists.01.org
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WARNING: multiple messages have this Message-ID (diff)
From: Yigal Korman <yigal@plexistor.com>
To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	x86@kernel.org, linux-kernel@vger.kernel.org
Cc: linux-nvdimm@ml01.01.org, dan.j.williams@intel.com,
	elliott@hpe.com, jmoyer@redhat.com, toshi.kani@hpe.com,
	Yigal Korman <yigal@plexistor.com>
Subject: [PATCH] x86/mm: only allow memmap=XX!YY over existing RAM
Date: Mon, 20 Jun 2016 10:33:59 +0300	[thread overview]
Message-ID: <1466408039-7497-1-git-send-email-yigal@plexistor.com> (raw)

Before this patch, passing a range that is beyond the physical memory
range will succeed, the user will see a /dev/pmem0 and will be able to
access it. Reads will always return 0 and writes will be silently
ignored.

I've gotten more than one bug report about mkfs.{xfs,ext4} or nvml
failing that were eventually tracked down to be wrong values passed to
memmap.

This patch prevents the above issue by instead of adding a new memory
range, only update a RAM memory range with the PRAM type. This way,
passing the wrong memmap will either not give you a pmem at all or give
you a smaller one that actually has RAM behind it.

And if someone still needs to fake a pmem that doesn't have RAM behind
it, they can simply do memmap=XX@YY,XX!YY.

Signed-off-by: Yigal Korman <yigal@plexistor.com>
---
 arch/x86/kernel/e820.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 621b501..4bd4207 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -878,7 +878,7 @@ static int __init parse_memmap_one(char *p)
 		e820_add_region(start_at, mem_size, E820_RESERVED);
 	} else if (*p == '!') {
 		start_at = memparse(p+1, &p);
-		e820_add_region(start_at, mem_size, E820_PRAM);
+		e820_update_range(start_at, mem_size, E820_RAM, E820_PRAM);
 	} else
 		e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
 
-- 
1.9.3

             reply	other threads:[~2016-06-20  7:35 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-20  7:33 Yigal Korman [this message]
2016-06-20  7:33 ` [PATCH] x86/mm: only allow memmap=XX!YY over existing RAM Yigal Korman
2016-06-20 14:44 ` Dan Williams
2016-06-20 14:44   ` Dan Williams
2016-06-21 12:56 ` Johannes Thumshirn
2016-06-21 12:56   ` Johannes Thumshirn
2016-06-23 11:52 ` Boaz Harrosh
2016-06-23 11:52   ` Boaz Harrosh

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