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Date: Thu, 7 Feb 2008 21:03:16 +0100
From: "Oliver Pinter" <oliver.pntr@...il.com>
To: "Linux Kernel" <linux-kernel@...r.kernel.org>, stable@...nel.org,
stable-commits@...r.kernel.org
Subject: [2.6.22.y] {03/14} - Handle bogus %cs selector in single-step instruction decoding - on top of 2.6.22.17
aka: handle-bogus-%cs-selector-in-single-step-instruction-decoding.patch
From: Roland McGrath <roland@...hat.com>
Date: Mon, 16 Jul 2007 08:03:16 +0000 (-0700)
Subject: Handle bogus %cs selector in single-step instruction decoding
Patch-mainline: 2.6.23-rc1
References: 326270, CVE-2007-3731
Handle bogus %cs selector in single-step instruction decoding
mainline: 29eb51101c02df517ca64ec472d7501127ad1da8
The code for LDT segment selectors was not robust in the face of a bogus
selector set in %cs via ptrace before the single-step was done.
Signed-off-by: Roland McGrath <roland@...hat.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Acked-by: Jeff Mahoney <jeffm@...e.com>
CC: Oliver Pinter <oliver.pntr@...il.com>
---
arch/i386/kernel/ptrace.c | 22 +++++++++++++++-------
arch/x86_64/kernel/ptrace.c | 23 ++++++++++++++++-------
2 files changed, 31 insertions(+), 14 deletions(-)
diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c
index 1c075f5..0c8f00e 100644
--- a/arch/i386/kernel/ptrace.c
+++ b/arch/i386/kernel/ptrace.c
@@ -164,14 +164,22 @@ static unsigned long
convert_eip_to_linear(struct task_struct *child, struct pt_
u32 *desc;
unsigned long base;
- down(&child->mm->context.sem);
- desc = child->mm->context.ldt + (seg & ~7);
- base = (desc[0] >> 16) | ((desc[1] & 0xff) << 16) | (desc[1] & 0xff000000);
+ seg &= ~7UL;
- /* 16-bit code segment? */
- if (!((desc[1] >> 22) & 1))
- addr &= 0xffff;
- addr += base;
+ down(&child->mm->context.sem);
+ if (unlikely((seg >> 3) >= child->mm->context.size))
+ addr = -1L; /* bogus selector, access would fault */
+ else {
+ desc = child->mm->context.ldt + seg;
+ base = ((desc[0] >> 16) |
+ ((desc[1] & 0xff) << 16) |
+ (desc[1] & 0xff000000));
+
+ /* 16-bit code segment? */
+ if (!((desc[1] >> 22) & 1))
+ addr &= 0xffff;
+ addr += base;
+ }
up(&child->mm->context.sem);
}
return addr;
diff --git a/arch/x86_64/kernel/ptrace.c b/arch/x86_64/kernel/ptrace.c
index fa6775e..e83cc67 100644
--- a/arch/x86_64/kernel/ptrace.c
+++ b/arch/x86_64/kernel/ptrace.c
@@ -102,16 +102,25 @@ unsigned long convert_rip_to_linear(struct
task_struct *child, struct pt_regs *r
u32 *desc;
unsigned long base;
- down(&child->mm->context.sem);
- desc = child->mm->context.ldt + (seg & ~7);
- base = (desc[0] >> 16) | ((desc[1] & 0xff) << 16) | (desc[1] & 0xff000000);
+ seg &= ~7UL;
- /* 16-bit code segment? */
- if (!((desc[1] >> 22) & 1))
- addr &= 0xffff;
- addr += base;
+ down(&child->mm->context.sem);
+ if (unlikely((seg >> 3) >= child->mm->context.size))
+ addr = -1L; /* bogus selector, access would fault */
+ else {
+ desc = child->mm->context.ldt + seg;
+ base = ((desc[0] >> 16) |
+ ((desc[1] & 0xff) << 16) |
+ (desc[1] & 0xff000000));
+
+ /* 16-bit code segment? */
+ if (!((desc[1] >> 22) & 1))
+ addr &= 0xffff;
+ addr += base;
+ }
up(&child->mm->context.sem);
}
+
return addr;
}
--
Thanks,
Oliver
--
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