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authorRoland McGrath <roland@redhat.com>2007-07-16 01:03:16 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-18 12:09:01 -0700
commit29eb51101c02df517ca64ec472d7501127ad1da8 (patch)
tree41101a87d0f895414f7e1a7c8676e54d1abedeea /arch/x86_64
parenta267c0a887064720dfab5775a4f09b20b4f8ec37 (diff)
downloadlinux-2.6.34-ux500-29eb51101c02df517ca64ec472d7501127ad1da8.tar.gz
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>
Diffstat (limited to 'arch/x86_64')
-rw-r--r--arch/x86_64/kernel/ptrace.c23
1 files changed, 16 insertions, 7 deletions
diff --git a/arch/x86_64/kernel/ptrace.c b/arch/x86_64/kernel/ptrace.c
index fa6775ef729..e83cc67155a 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;
}