From: Willy Tarreau <w@1wt.eu>
To: Ben Hutchings <ben@decadent.org.uk>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
Andy Lutomirski <luto@amacapital.net>,
Andi Kleen <andi@firstfloor.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [ 05/48] x86_64, switch_to(): Load TLS descriptors before switching DS and ES
Date: Fri, 15 May 2015 16:37:24 +0200 [thread overview]
Message-ID: <20150515143724.GA31155@1wt.eu> (raw)
In-Reply-To: <1431699933.6315.115.camel@decadent.org.uk>
On Fri, May 15, 2015 at 03:25:33PM +0100, Ben Hutchings wrote:
> On Fri, 2015-05-15 at 15:38 +0200, Willy Tarreau wrote:
> > Hi Ben,
> >
> > On Fri, May 15, 2015 at 01:32:20PM +0100, Ben Hutchings wrote:
> > > On Fri, 2015-05-15 at 10:05 +0200, Willy Tarreau wrote:
> > > > 2.6.32-longterm review patch. If anyone has any objections, please let me know.
> > > >
> > > > ------------------
> > > >
> > > > From: Andy Lutomirski <luto@amacapital.net>
> > > >
> > > > commit f647d7c155f069c1a068030255c300663516420e upstream.
> > > >
> > > > Otherwise, if buggy user code points DS or ES into the TLS
> > > > array, they would be corrupted after a context switch.
> > > >
> > > > This also significantly improves the comments and documents some
> > > > gotchas in the code.
> > > >
> > > > Before this patch, the both tests below failed. With this
> > > > patch, the es test passes, although the gsbase test still fails.
> > > [...]
> > >
> > > This depends on the changes to FPU/MMX/SSE state management that you
> > > didn't apply to 2.6.32. Note this comment:
> > >
> > > /* Must be after DS reload */
> > > unlazy_fpu(prev_p);
> >
> > Are you sure you're not confusing with another one ? When running
> > estest without this patch, I get "FAIL: ES corrupted 1000/1000 times"
> > while I get "OK: ES was preserved" once applied, so it does seem to
> > do what it's intended for.
> >
> > Also I'm not seeing any reference to the comment above in the patch
> > nor around it, which leaves me confused :-/
>
> v2.6.32.65:arch/x86/kernel/process_64.c:425: /* Must be after DS reload */
Ah OK I missed it, thanks.
> If this comment is correct then the patch will cause a regression for
> FPU state management. The comment was introduced by:
>
> commit 0a5ace2ab08d45cd78d7ef0067cdcd5c812ac54f
> Author: Andi Kleen <ak@suse.de>
> Date: Thu Oct 5 18:47:22 2006 +0200
>
> [PATCH] x86-64: Fix FPU corruption
Indeed! Andy, is there any practical case covered by your patch that
should motivate a safe way to backport it, or can we simply drop it
for 2.6.32 ? I don't intend to backport the FPU state management
series that late in the cycle just for this!
Thanks!
Willy
next prev parent reply other threads:[~2015-05-15 14:37 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <9c2783dfae10ef2d1e9b08bcc1e562c5@local>
2015-05-15 8:05 ` [ 00/48] 2.6.32.66-longterm review Willy Tarreau
2015-05-15 8:05 ` [ 01/48] x86/asm/traps: Disable tracing and kprobes in fixup_bad_iret and sync_regs Willy Tarreau
2015-05-15 8:05 ` [ 02/48] x86/tls: Validate TLS entries to protect espfix Willy Tarreau
2015-05-15 8:05 ` [ 03/48] x86, tls, ldt: Stop checking lm in LDT_empty Willy Tarreau
2015-05-15 8:05 ` [ 04/48] x86, tls: Interpret an all-zero struct user_desc as "no segment" Willy Tarreau
2015-05-15 8:05 ` [ 05/48] x86_64, switch_to(): Load TLS descriptors before switching DS and ES Willy Tarreau
2015-05-15 12:32 ` Ben Hutchings
2015-05-15 13:38 ` Willy Tarreau
2015-05-15 14:25 ` Ben Hutchings
2015-05-15 14:31 ` Ben Hutchings
2015-05-15 14:37 ` Willy Tarreau [this message]
2015-05-15 15:53 ` Andi Kleen
2015-05-15 16:48 ` Willy Tarreau
2015-05-15 20:53 ` Ben Hutchings
2015-05-15 22:15 ` Andi Kleen
2015-05-15 8:05 ` [ 06/48] x86/tls: Disallow unusual TLS segments Willy Tarreau
2015-05-15 8:05 ` [ 07/48] x86/tls: Dont validate lm in set_thread_area() after all Willy Tarreau
2015-05-15 8:05 ` [ 08/48] x86, kvm: Clear paravirt_enabled on KVM guests for espfix32s benefit Willy Tarreau
2015-05-15 8:05 ` [ 09/48] x86_64, vdso: Fix the vdso address randomization algorithm Willy Tarreau
2015-05-15 21:02 ` Ben Hutchings
2015-05-15 8:05 ` [ 10/48] ASLR: fix stack randomization on 64-bit systems Willy Tarreau
2015-05-15 8:05 ` [ 11/48] x86, cpu, amd: Add workaround for family 16h, erratum 793 Willy Tarreau
2015-05-15 8:05 ` [ 12/48] x86/asm/entry/64: Remove a bogus ret_from_fork optimization Willy Tarreau
2015-05-15 8:05 ` [ 13/48] x86: Conditionally update time when ack-ing pending irqs Willy Tarreau
2015-05-15 8:05 ` [ 14/48] serial: samsung: wait for transfer completion before clock disable Willy Tarreau
2015-05-15 8:05 ` [ 15/48] splice: Apply generic position and size checks to each write Willy Tarreau
2015-05-15 8:05 ` [ 16/48] netfilter: conntrack: disable generic tracking for known protocols Willy Tarreau
2015-05-15 21:05 ` Ben Hutchings
2015-05-15 8:05 ` [ 17/48] isofs: Fix infinite looping over CE entries Willy Tarreau
2015-05-15 8:05 ` [ 18/48] isofs: Fix unchecked printing of ER records Willy Tarreau
2015-05-15 8:05 ` [ 19/48] net: sctp: fix memory leak in auth key management Willy Tarreau
2015-05-15 8:05 ` [ 20/48] net: sctp: fix slab corruption from use after free on INIT collisions Willy Tarreau
2015-05-15 8:05 ` [ 21/48] IB/uverbs: Prevent integer overflow in ib_umem_get address arithmetic Willy Tarreau
2015-05-15 8:05 ` [ 22/48] net: llc: use correct size for sysctl timeout entries Willy Tarreau
2015-05-15 8:05 ` [ 23/48] net: rds: use correct size for max unacked packets and bytes Willy Tarreau
2015-05-15 8:05 ` [ 24/48] ipv6: Dont reduce hop limit for an interface Willy Tarreau
2015-05-15 8:05 ` [ 25/48] fs: take i_mutex during prepare_binprm for set[ug]id executables Willy Tarreau
2015-05-15 8:05 ` [ 26/48] net:socket: set msg_namelen to 0 if msg_name is passed as NULL in msghdr struct from userland Willy Tarreau
2015-05-15 21:08 ` Ben Hutchings
2015-05-16 5:31 ` Willy Tarreau
2015-05-15 8:05 ` [ 27/48] ppp: deflate: never return len larger than output buffer Willy Tarreau
2015-05-15 8:05 ` [ 29/48] net: reject creation of netdev names with colons Willy Tarreau
2015-05-15 8:06 ` [ 30/48] ipv4: Dont use ufo handling on later transformed packets Willy Tarreau
2015-05-15 8:06 ` [ 31/48] udp: only allow UFO for packets from SOCK_DGRAM sockets Willy Tarreau
2015-05-15 8:06 ` [ 32/48] net: avoid to hang up on sending due to sysctl configuration overflow Willy Tarreau
2015-05-15 8:06 ` [ 33/48] net: sysctl_net_core: check SNDBUF and RCVBUF for min length Willy Tarreau
2015-05-15 8:06 ` [ 34/48] rds: avoid potential stack overflow Willy Tarreau
2015-05-15 8:06 ` [ 35/48] rxrpc: bogus MSG_PEEK test in rxrpc_recvmsg() Willy Tarreau
2015-05-15 8:06 ` [ 36/48] tcp: make connect() mem charging friendly Willy Tarreau
2015-05-15 8:06 ` [ 37/48] ip_forward: Drop frames with attached skb->sk Willy Tarreau
2015-05-15 8:06 ` [ 38/48] tcp: avoid looping in tcp_send_fin() Willy Tarreau
2015-05-15 8:06 ` [ 39/48] spi: spidev: fix possible arithmetic overflow for multi-transfer message Willy Tarreau
2015-05-15 8:06 ` [ 40/48] IB/core: Avoid leakage from kernel to user space Willy Tarreau
2015-05-15 8:06 ` [ 41/48] ipvs: uninitialized data with IP_VS_IPV6 Willy Tarreau
2015-05-15 8:06 ` [ 42/48] ipv4: fix nexthop attlen check in fib_nh_match Willy Tarreau
2015-05-15 8:06 ` [ 43/48] pagemap: do not leak physical addresses to non-privileged userspace Willy Tarreau
2015-05-15 8:06 ` [ 44/48] lockd: Try to reconnect if statd has moved Willy Tarreau
2015-05-15 8:06 ` [ 45/48] scsi: Fix error handling in SCSI_IOCTL_SEND_COMMAND Willy Tarreau
2015-05-15 8:06 ` [ 46/48] posix-timers: Fix stack info leak in timer_create() Willy Tarreau
2015-05-15 8:06 ` [ 47/48] hfsplus: fix B-tree corruption after insertion at position 0 Willy Tarreau
2015-05-15 8:06 ` [ 48/48] sound/oss: fix deadlock in sequencer_ioctl(SNDCTL_SEQ_OUTOFBAND) Willy Tarreau
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