tree 174f2ba42679903c0178f1a684adcad893e18b4e
parent 2d5a5612bceda8edd25b29f363c4e2c6cda28bab
author Will Deacon <will.deacon@arm.com> 1401706043 +0100
committer Catalin Marinas <catalin.marinas@arm.com> 1403091657 +0100

arm64: ptrace: change fs when passing kernel pointer to regset code

Our compat PTRACE_POKEUSR implementation simply passes the user data to
regset_copy_from_user after some simple range checking. Unfortunately,
the data in question has already been copied to the kernel stack by this
point, so the subsequent access_ok check fails and the ptrace request
returns -EFAULT. This causes problems tracing fork() with older versions
of strace.

This patch briefly changes the fs to KERNEL_DS, so that the access_ok
check passes even with a kernel address.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>