From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Emelyanov Subject: Re: [PATCH] autofs4: fix 32-bit userspace vs 64-bit kernel communications Date: Wed, 11 Jun 2008 16:47:10 +0400 Message-ID: <484FC94E.1000209@openvz.org> References: <484FA0B8.2000002@openvz.org> <1213187579.4994.25.camel@raven.themaw.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1213187579.4994.25.camel@raven.themaw.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Ian Kent Cc: autofs mailing list , Linux Kernel Mailing List , Konstantin Khlebnikov Ian Kent wrote: > On Wed, 2008-06-11 at 13:54 +0400, Pavel Emelyanov wrote: >> From: Konstantin Khlebnikov >> >> The struct autofs_v5_packet has only one difference between >> 32-bit and 64-bit versions - on 64-bit gcc aligns its size and >> it is 4 bytes larger that it is on 32-bit kernel. This confuses >> 32-bit user-space daemon, when talking to 64-bit kernel. > > No, I don't think that's quite right. > > As far as I know this issue arises when a user space program, compiled > as a 32-bit application is executed within 64-bit user space. What program do mean here? The problem arises right on the kernel-daemon boundary - the latter refuses to accept the message with larger length. No other software required. >> This is very critical for containerized setups, when containers >> with -bit tolls are used. > > Have you tested different situations with this change? > Will this affect the existing check and adjustment the version 5 > automount daemon does now? 64-bit daemons *still* work OK and 32-bit *start* to after this fix :) >> Signed-off-by: Konstantin Khlebnikov >> Acked-by: Pavel Emelyanov >> >> --- >> >> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c >> index 1e4a539..9855b6e 100644 >> --- a/fs/autofs4/waitq.c >> +++ b/fs/autofs4/waitq.c >> @@ -132,6 +132,14 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi, >> struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet; >> >> pktsz = sizeof(*packet); >> +#if defined(CONFIG_X86_64) && defined(CONFIG_IA32_EMULATION) >> + /* >> + * On x86_64 autofs_v5_packet struct is padded with 4 bytes >> + * which breaks 32-bit autofs daemon. >> + */ >> + if (test_thread_flag(TIF_IA32)) >> + pktsz -= 4; >> +#endif >> >> packet->wait_queue_token = wq->wait_queue_token; >> packet->len = wq->len; >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >