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From: Roland McGrath <roland@redhat.com>
Date: Mon, 16 Jul 2007 08:03:16 +0000 (-0700)
Subject: Handle bogus %cs selector in single-step instruction decoding
X-Git-Tag: v2.6.23-rc1~492
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=29eb51101c02df517ca64ec472d7501127ad1da8
Handle bogus %cs selector in single-step instruction decoding
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@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
Adjusted to apply to Debian's 2.6.18 by dann frazier <dannf@debian.org>
diff -urpN linux-source-2.6.18.orig/arch/i386/kernel/ptrace.c linux-source-2.6.18/arch/i386/kernel/ptrace.c
--- linux-source-2.6.18.orig/arch/i386/kernel/ptrace.c 2006-09-19 21:42:06.000000000 -0600
+++ linux-source-2.6.18/arch/i386/kernel/ptrace.c 2007-09-19 23:45:45.949576125 -0600
@@ -172,14 +172,22 @@ static unsigned long convert_eip_to_line
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 -urpN linux-source-2.6.18.orig/arch/x86_64/kernel/ptrace.c linux-source-2.6.18/arch/x86_64/kernel/ptrace.c
--- linux-source-2.6.18.orig/arch/x86_64/kernel/ptrace.c 2006-09-19 21:42:06.000000000 -0600
+++ linux-source-2.6.18/arch/x86_64/kernel/ptrace.c 2007-09-19 23:45:45.953575027 -0600
@@ -103,16 +103,25 @@ unsigned long convert_rip_to_linear(stru
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;
}
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