Messages in this thread | | | Date | Thu, 12 Feb 2015 08:41:24 -0800 (PST) | Subject | Re: [PATCH] net: compat: Ignore MSG_CMSG_COMPAT in compat_sys_{send,recv}msg | From | David Miller <> |
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From: Catalin Marinas <catalin.marinas@arm.com> Date: Thu, 12 Feb 2015 12:28:07 +0000
> With commit a7526eb5d06b (net: Unbreak compat_sys_{send,recv}msg), the > MSG_CMSG_COMPAT flag is blocked at the compat syscall entry points, > changing the kernel compat behaviour from the one before the commit it > was trying to fix (1be374a0518a, net: Block MSG_CMSG_COMPAT in > send(m)msg and recv(m)msg). > > On 32-bit kernels (!CONFIG_COMPAT), MSG_CMSG_COMPAT is 0 and the native > 32-bit sys_sendmsg() allows flag 0x80000000 to be set (it is ignored by > the kernel). However, on a 64-bit kernel, the compat ABI is different > with commit a7526eb5d06b. > > This patch changes the compat_sys_{send,recv}msg behaviour to the one > prior to commit 1be374a0518a. > > The problem was found running 32-bit LTP (sendmsg01) binary on an arm64 > kernel. Arguably, LTP should not pass 0xffffffff as flags to sendmsg() > but the general rule is not to break user ABI (even when the user > behaviour is not entirely sane). > > Fixes: a7526eb5d06b (net: Unbreak compat_sys_{send,recv}msg) > Cc: Andy Lutomirski <luto@amacapital.net> > Cc: David S. Miller <davem@davemloft.net> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
I think this is a very poor LTP test.
Setting MSG_* bits that aren't supported by the protocol in any way gives undefined semantics. You may get an error, it may be silently ignored, etc.
I'm not applying this, sorry.
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