From: Ingo Molnar <mingo@kernel.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org, bristot@redhat.com,
jbaron@akamai.com, torvalds@linux-foundation.org,
tglx@linutronix.de, namit@vmware.com, hpa@zytor.com,
luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com,
jeyu@kernel.org
Subject: Re: [PATCH -tip 2/2] kprobes: Set unoptimized flag after unoptimizing code
Date: Wed, 27 Nov 2019 07:49:04 +0100 [thread overview]
Message-ID: <20191127064904.GA52731@gmail.com> (raw)
In-Reply-To: <20191127061910.nbfmzds4k5wxorwz@ast-mbp.dhcp.thefacebook.com>
* Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> On Wed, Nov 27, 2019 at 02:57:04PM +0900, Masami Hiramatsu wrote:
> > Fix to set unoptimized flag after confirming the code is completely
> > unoptimized. Without this fix, when a kprobe hits the intermediate
> > modified instruction (the first byte is replaced by int3, but
> > latter bytes still be a jump address operand) while unoptimizing,
> > it can return to the middle byte of the modified code. And it causes
> > an invalid instruction exception in the kernel.
> >
> > Usually, this is a rare case, but if we put a probe on the function
> > called while text patching, it always causes a kernel panic as below.
> > (text_poke() is used for patching the code in optprobe)
> >
> > # echo p text_poke+5 > kprobe_events
> > # echo 1 > events/kprobes/enable
> > # echo 0 > events/kprobes/enable
> > invalid opcode: 0000 [#1] PREEMPT SMP PTI
> > CPU: 7 PID: 137 Comm: kworker/7:1 Not tainted 5.4.0-rc8+ #29
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
> > Workqueue: events kprobe_optimizer
> > RIP: 0010:text_poke+0x9/0x50
> > Code: 01 00 00 5b 5d 41 5c 41 5d c3 89 c0 0f b7 4c 02 fe 66 89 4c 05 fe e9 31 ff ff ff e8 71 ac 03 00 90 55 48 89 f5 53 cc 30 cb fd <1e> ec 08 8b 05 72 98 31 01 85 c0 75 11 48 83 c4 08 48 89 ee 48 89
> > RSP: 0018:ffffc90000343df0 EFLAGS: 00010686
> > RAX: 0000000000000000 RBX: ffffffff81025796 RCX: 0000000000000000
> > RDX: 0000000000000004 RSI: ffff88807c983148 RDI: ffffffff81025796
> > RBP: ffff88807c983148 R08: 0000000000000001 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff82284fe0
> > R13: ffff88807c983138 R14: ffffffff82284ff0 R15: 0ffff88807d9eee0
> > FS: 0000000000000000(0000) GS:ffff88807d9c0000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 000000000058158b CR3: 000000007b372000 CR4: 00000000000006a0
> > Call Trace:
> > arch_unoptimize_kprobe+0x22/0x28
> > arch_unoptimize_kprobes+0x39/0x87
> > kprobe_optimizer+0x6e/0x290
> > process_one_work+0x2a0/0x610
> > worker_thread+0x28/0x3d0
> > ? process_one_work+0x610/0x610
> > kthread+0x10d/0x130
> > ? kthread_park+0x80/0x80
> > ret_from_fork+0x3a/0x50
> > Modules linked in:
> > ---[ end trace 83b34b22a228711b ]---
> >
> > This can happen even if we blacklist text_poke() and other functions,
> > because there is a small time window which showing the intermediate
> > code to other CPUs.
> >
> > Fixes: 6274de4984a6 ("kprobes: Support delayed unoptimizing")
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
>
> Awesome. It fixes the crash for me.
> Tested-by: Alexei Starovoitov <ast@kernel.org>
Thanks guys - I just pushed out a rebased tree, based on an upstream
version that has both the BPF tree and most x86 trees merged, into
tip:WIP.core/kprobes. This includes these two fixes as well.
Thanks,
Ingo
next prev parent reply other threads:[~2019-11-27 6:49 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 5:56 [PATCH -tip 0/2] x86/kprobes: Fix 2 issues related to text_poke_bp and optprobe Masami Hiramatsu
2019-11-27 5:56 ` [PATCH -tip 1/2] x86/alternative: Sync bp_patching update for avoiding NULL pointer exception Masami Hiramatsu
2019-12-02 9:15 ` Peter Zijlstra
2019-12-02 11:50 ` Masami Hiramatsu
2019-12-02 13:43 ` Peter Zijlstra
2019-12-02 14:39 ` Masami Hiramatsu
2019-12-04 8:33 ` [tip: core/kprobes] x86/alternatives: " tip-bot2 for Masami Hiramatsu
2019-12-09 14:39 ` [PATCH -tip 1/2] x86/alternative: " Peter Zijlstra
2019-12-10 16:44 ` Masami Hiramatsu
2019-12-10 17:32 ` Peter Zijlstra
2019-12-11 0:09 ` Peter Zijlstra
2019-12-11 8:09 ` Masami Hiramatsu
2019-12-11 9:12 ` Daniel Bristot de Oliveira
2019-11-27 5:57 ` [PATCH -tip 2/2] kprobes: Set unoptimized flag after unoptimizing code Masami Hiramatsu
2019-11-27 6:19 ` Alexei Starovoitov
2019-11-27 6:49 ` Ingo Molnar [this message]
2019-12-02 21:55 ` Alexei Starovoitov
2019-11-27 6:56 ` Masami Hiramatsu
2019-12-04 8:33 ` [tip: core/kprobes] " tip-bot2 for Masami Hiramatsu
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