From: Roland McGrath <roland@redhat.com>
Date: Tue, 14 Sep 2010 19:22:58 +0000 (-0700)
Subject: x86-64, compat: Retruncate rax after ia32 syscall entry tracing
X-Git-Tag: v2.6.27.54~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1b159e074a425d80c9cff0f19404a9fbe83140a5;p=pandora-kernel.git

x86-64, compat: Retruncate rax after ia32 syscall entry tracing

commit eefdca043e8391dcd719711716492063030b55ac upstream.

In commit d4d6715, we reopened an old hole for a 64-bit ptracer touching a
32-bit tracee in system call entry.  A %rax value set via ptrace at the
entry tracing stop gets used whole as a 32-bit syscall number, while we
only check the low 32 bits for validity.

Fix it by truncating %rax back to 32 bits after syscall_trace_enter,
in addition to testing the full 64 bits as has already been added.

Reported-by: Ben Hawkes <hawkes@sota.gen.nz>
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

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