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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
	Ard Biesheuvel <ardb@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 4.9 6/9] x86/boot: Use unsigned comparison for addresses
Date: Thu,  9 Apr 2020 23:51:07 -0400	[thread overview]
Message-ID: <20200410035111.9938-6-sashal@kernel.org> (raw)
In-Reply-To: <20200410035111.9938-1-sashal@kernel.org>

From: Arvind Sankar <nivedita@alum.mit.edu>

[ Upstream commit 81a34892c2c7c809f9c4e22c5ac936ae673fb9a2 ]

The load address is compared with LOAD_PHYSICAL_ADDR using a signed
comparison currently (using jge instruction).

When loading a 64-bit kernel using the new efi32_pe_entry() point added by:

  97aa276579b2 ("efi/x86: Add true mixed mode entry point into .compat section")

using Qemu with -m 3072, the firmware actually loads us above 2Gb,
resulting in a very early crash.

Use the JAE instruction to perform a unsigned comparison instead, as physical
addresses should be considered unsigned.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200301230436.2246909-6-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-14-ardb@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/boot/compressed/head_32.S | 2 +-
 arch/x86/boot/compressed/head_64.S | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index fd0b6a272dd5b..7532f6f536774 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -170,7 +170,7 @@ preferred_addr:
 	notl	%eax
 	andl    %eax, %ebx
 	cmpl	$LOAD_PHYSICAL_ADDR, %ebx
-	jge	1f
+	jae	1f
 #endif
 	movl	$LOAD_PHYSICAL_ADDR, %ebx
 1:
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 9e3a183561a9a..3fac2d133e4ec 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -104,7 +104,7 @@ ENTRY(startup_32)
 	notl	%eax
 	andl	%eax, %ebx
 	cmpl	$LOAD_PHYSICAL_ADDR, %ebx
-	jge	1f
+	jae	1f
 #endif
 	movl	$LOAD_PHYSICAL_ADDR, %ebx
 1:
@@ -339,7 +339,7 @@ preferred_addr:
 	notq	%rax
 	andq	%rax, %rbp
 	cmpq	$LOAD_PHYSICAL_ADDR, %rbp
-	jge	1f
+	jae	1f
 #endif
 	movq	$LOAD_PHYSICAL_ADDR, %rbp
 1:
-- 
2.20.1


  parent reply	other threads:[~2020-04-10  3:51 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-10  3:51 [PATCH AUTOSEL 4.9 1/9] irqchip/versatile-fpga: Handle chained IRQs properly Sasha Levin
2020-04-10  3:51 ` [PATCH AUTOSEL 4.9 2/9] sched: Avoid scale real weight down to zero Sasha Levin
2020-04-10  3:51 ` [PATCH AUTOSEL 4.9 3/9] selftests/x86/ptrace_syscall_32: Fix no-vDSO segfault Sasha Levin
2020-04-10  3:51 ` [PATCH AUTOSEL 4.9 4/9] libata: Remove extra scsi_host_put() in ata_scsi_add_hosts() Sasha Levin
2020-04-10  3:51 ` [PATCH AUTOSEL 4.9 5/9] gfs2: Don't demote a glock until its revokes are written Sasha Levin
2020-04-10  3:51 ` Sasha Levin [this message]
2020-04-10  3:51 ` [PATCH AUTOSEL 4.9 7/9] locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps() Sasha Levin
2020-04-10  3:51 ` [PATCH AUTOSEL 4.9 8/9] btrfs: remove a BUG_ON() from merge_reloc_roots() Sasha Levin
2020-04-10  3:51 ` [PATCH AUTOSEL 4.9 9/9] btrfs: track reloc roots based on their commit root bytenr Sasha Levin

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