From: Michael Ellerman <mpe@ellerman.id.au>
Date: Thu, 23 Jul 2015 10:21:07 +0000 (+1000)
Subject: powerpc: Change syscall_get_nr() to return int
X-Git-Tag: omap-for-v4.3/fixes-rc1~100^2~78
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e9fbe6863281b942d7eea44c6ccabc30f46ab44f;p=pandora-kernel.git

powerpc: Change syscall_get_nr() to return int

The documentation for syscall_get_nr() in asm-generic says:

 Note this returns int even on 64-bit machines. Only 32 bits of
 system call number can be meaningful. If the actual arch value
 is 64 bits, this truncates to 32 bits so 0xffffffff means -1.

However our implementation was never updated to reflect this.

Generally it's not important, but there is once case where it matters.

For seccomp filter with SECCOMP_RET_TRACE, the tracer will set
regs->gpr[0] to -1 to reject the syscall. When the task is a compat
task, this means we end up with 0xffffffff in r0 because ptrace will
zero extend the 32-bit value.

If syscall_get_nr() returns an unsigned long, then a 64-bit kernel will
see a positive value in r0 and will incorrectly allow the syscall
through seccomp.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Kees Cook <keescook@chromium.org>
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