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um: Fix PTRACE_POKEUSER on x86_64

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commit 9abc74a22d upstream.

This is broken since ever but sadly nobody noticed.
Recent versions of GDB set DR_CONTROL unconditionally and
UML dies due to a heap corruption. It turns out that
the PTRACE_POKEUSER was copy&pasted from i386 and assumes
that addresses are 4 bytes long.

Fix that by using 8 as address size in the calculation.

Reported-by: jie cao <cj3054@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Richard Weinberger 2017-04-01 00:41:57 +02:00 committed by Greg Kroah-Hartman
parent b8cd9dd513
commit a2d5dcf338
1 changed files with 1 additions and 1 deletions
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2
arch/x86/um/ptrace_64.c
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@ -121,7 +121,7 @@ int poke_user(struct task_struct *child, long addr, long data)
else if ((addr >= offsetof(struct user, u_debugreg[0])) &&
(addr <= offsetof(struct user, u_debugreg[7]))) {
addr -= offsetof(struct user, u_debugreg[0]);
addr = addr >> 2;
addr = addr >> 3;
if ((addr == 4) || (addr == 5))
return -EIO;
child->thread.arch.debugregs[addr] = data;