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

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commit c168870704 upstream.

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>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Will Deacon 2014-06-02 11:47:23 +01:00 • committed by Greg Kroah-Hartman

parent 3d672e43c3

commit 993e3e1656

1 changed files with 4 additions and 0 deletions

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arch/arm64/kernel/ptrace.c

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