From 29eb51101c02df517ca64ec472d7501127ad1da8 Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Mon, 16 Jul 2007 01:03:16 -0700 Subject: 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 Signed-off-by: Linus Torvalds --- arch/i386/kernel/ptrace.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) (limited to 'arch/i386/kernel/ptrace.c') diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c index 1c075f58d1f..0c8f00e69c4 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; -- cgit v1.2.3