Messages in this thread Patch in this message | | | Date | Tue, 29 Jan 2008 00:13:37 +0100 | From | "Oliver Pinter (Pintér Olivér)" <> | Subject | [2.6.22.y] {06/17} - handle-bogus-%cs-selector-in-single-step-instruction-decoding - series for stable kernel |
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-- Thanks, Oliver commit d16cb86e71908ec86addc7f1c0934d00cfbc55ed Author: Roland McGrath <roland@redhat.com> Date: Mon Jul 16 08:03:16 2007 -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
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> Acked-by: Jeff Mahoney <jeffm@suse.com>
diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c index 0c0ceec..120a63b 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 8d89d8c..7fc0e73 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; } | |